herbicidal weed control methods for pastures and …...herbicidal weed control methods for pastures...

Herbicidal WeedControl Methodsfor Pastures andNatural Areasof Hawaii

Philip Motooka1, Lincoln Ching2, and Guy Nagai3

1,2CTAHR Departments of 1Natural Resources and Environmental Management and 2Human Nutrition, Food and Animal Sciences3Hawaii Department of Agriculture

Weed ControlNov. 2002—WC-8

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Herbicidal Weed Control Methods for Pastures and Natural Areas of Hawaii

Methods of weed control ............................................ 3Quarantine and sanitation ........................................ 3Biocontrol ................................................................ 4Cultural control ....................................................... 4Mechanical or manual control ................................. 4Herbicides................................................................ 5Herbicide hazards in perspective............................. 5

Methods of herbicide application ............................... 6

Conventional foliar methods ................................... 6Choice of herbicide .............................................. 6Herbicide selectivity ............................................ 7Herbicide persistence ........................................... 7Herbicide formulations ........................................ 7Surfactants ............................................................ 8Rates of application .............................................. 8Coverage .............................................................. 8Spray volume rates ............................................... 8Timeliness ............................................................ 9Integrated treatments ............................................ 9Drift prevention .................................................. 10Calibration of spray volume rate and

herbicide concentration ............................... 10Boom sprayer .................................................. 11Power sprayer, orchard gun method ............... 11Knapsack sprayer ............................................ 11

Drizzle foliar application ....................................... 12

Logistics limit conventional spraying ................ 12The drizzle method ............................................ 12Efficiency of the drizzle method ........................ 14Other advantages ................................................ 14Limitations of the drizzle method ...................... 14Calibration .......................................................... 14Table 1. Herbicides for drizzle application ........ 15Drizzle foliar application, water carrier ............. 16Drizzle foliar application, crop oil carrier .......... 16

Cut-surface methods .............................................. 16Notching ............................................................. 16Cut-stump method .............................................. 18Basal bark method .............................................. 19Very-low-volume basal bark and

stump applications .......................................... 20

Soil-applied herbicides .......................................... 20

Appendix 1. Herbicides registered for use inpastures and natural areas of Hawaii ................. 23

Table A-1. The rating scale of toxins andexample substances ............................................ 25

Table A-2. Pesticide toxicity signal words andapproximate lethal dose ..................................... 25

Appendix 2. Common and botanical names ofweeds mentioned in the text .................................. 32

Literature cited .......................................................... 33

Table of Contents

AcknowledgmentsMany colleagues participated in the field work that gener-ated the information presented here. Many hours of work inthe hot sun or pouring rain are represented in a single recom-mendation. From the UH CTAHR Cooperative ExtensionService: Mike DuPonte and Andrew Kawabata, Hilo; GlenFukumoto, Kona; John Powley, Maui; Alton Arakaki andGlenn Teves, Molokai. From the Hawaii Department of Ag-riculture: Guy Nagai (retired), Kauai; Kyle Onuma and WayneShishido (retired), Hilo. From the Hawaii Department of Landand Natural Resources, Division of Forestry and Wildlife:Ed Pettys, Alvin Kiyono, Craig Koga, Galen Kawakami, andSanford Soto, Kauai; Glenn Shishido and Fern Duvall, Maui.

Many others in both the public and private sectors par-ticipated occasionally. Many ranchers and other landown-ers and land managers allowed access to their lands.DowAgrosciences, DuPonte De Nemours, American Cy-

anamid, BASF, Monsanto, PBI Gordon, United HortculturalSupply, and Brewer Environmental Industries furnishedneeded supplies. Drs. Roy Nishimoto and J.B. Friday(CTAHR) ably reviewed the manuscript, and Dale Evansedited and produced the finished publication. Finally, thecontribution of funds to publish this document was gener-ously provided by several organizations: the Institute ofPacific Islands Forestry, Forest Service, U.S. Departmentof Agriculture; the Big Island Invasive Species Committeeand the Division of Forestry and Wildlife of the HawaiiDepartment of Land and Natural Resources; the U.S. Na-tional Park Service Pacific Islands Exotic Plant Manage-ment Team and the Maui Invasive Species Committee; theUSDA Natural Resources Conservation Service and the Eastand West Kauai Soil and Water Conservation Districts. Allof these contributions are gratefully acknowledged.

Neither the University of Hawaii, the College of Tropical Agriculture and Human Resources, nor the authors shall be liable for any damagesresulting from the use of or reliance on the information contained in this publication, or from any omissions to it. Mention of a trademark, company,or proprietary name does not constitute an endorsement, guarantee, or warranty by the University of Hawaii Cooperative Extension Service or itsemployees and does not imply recommendation to the exclusion of other suitable products or companies. Pesticide use is governed by state andfederal regulations. Read the pesticide label to ensure that the intended use is included on it, and follow all label directions.

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The severity of the impact of weeds on ranching andforest management is often underestimated. Besides

competing with forage plants for soil nutrients, sunlight,and water, and thereby suppressing forage growth, weedsalso create management problems.

For example, brush in Texas used up over two timesthe water requirements of all the cities and industries inthat state in 1980(32). Many weeds are poisonous, orarmed with spines that may injure animals directly orby leading to infections. Mesquite (Prosopis spp.) in-festations in Arizona suppressed forage growth and pro-moted soil erosion and rain runoff(66). On brush-infestedranches, cattle are more skittish, requiring more laborto manage; more bulls are required to service the herd;newborn calves instinctively remain in hiding as mow-ers approach and may be killed. Another Texas studyindicated that brush-free ranches could stock 42 percentmore animals and would need 59 percent less perma-nent labor and 58 percent less labor at roundup(34). Weedsalso threaten native plant communities in forests andshrublands and, thereby, the native animals dependenton the specific native plants or complex of plants thatmake up that plant community. The original ecosystemis thus replaced by a new, exotic one(10).

Weeds are often more competitive than native plantsbecause of a lack of natural controls such as diseasesand predators. Many are able to suppress plants grow-ing close to them by producing growth retardants. Indi-rectly, they suppress natives by supporting wildfires,which may be devastating to native plants but whichmay be natural to alien species; they may fix nitrogen,which alien species may be better able to utilize thannatives(102). The ecology of natural areas worldwide isthreatened by invasive weeds. Thus weed management

is an on-going problem for ranchers, foresters, and otherland managers.

Use of herbicides is an effective and efficient meansof managing weeds. Contrary to popular perception, itis also very safe. In many cases there are no practicalalternatives to chemical weed control methods. How-ever, herbicides can easily be misused and inflict unin-tended injury to non-target organisms. In order to en-sure efficacy, efficiency, and economy—and non-targetsafety—users of herbicides must have an understand-ing of herbicide application principles and plant re-sponses to herbicides.

Methods of weed controlPrehistoric humans saw the need to deal with weeds.Nearly 3000 years ago, people in Europe cleared treesand brush from around oak and nut trees to increase thesize and number of acorns and nuts(21). Throughout his-tory, many methods of control have been devised, all ofwhich are still used today. While this publication dealswith chemical methods of weed management, one ormore of the other methods are often used in conjunctionwith chemical methods. Several of these methods re-quire the authority and resources of the government (e.g.,quarantine and biocontrol). Others are in the hands ofthe herbicide user (e.g., mechanical methods). Becausean understanding of the other methods can be helpful indeveloping comprehensive weed management strategies,they are briefly described in the following paragraphs.

Quarantine and sanitationThe most economical method of weed control is pre-vention. Weed species are prevented from moving intouncontaminated areas by quarantine, the official regu-

Herbicidal Weed Control Methodsfor Pastures and Natural Areas of Hawaii

Philip Motooka, Lincoln Ching, and Guy Nagai

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lation of weed movement across political borders, andby sanitation, the unofficial control of weed movement(e.g., cleaning shoes and clothing between hikes andcorraling livestock for a time between infested pasturesand uninfested pastures). Unfortunately, with increas-ing worldwide commerce, preventing weed movementis becoming more difficult. New weeds and other pestsdo get by quarantine, either deliberately or inadvertently.

One of the problems is that weediness is unpredict-able. A noxious weed in one area can be benign in an-other. A further difficulty is that many alien plant intro-ductions may be benign for years or decades before sud-denly exploding into a serious weed pest(17). There areongoing attempts to characterize weediness so that quar-antine can be made more effective and efficient. It hasbeen suggested that some of the characteristics that de-termine weediness include short cycles between seedings,production of many seeds, small seeds, seed dispersal byvertebrates, adaptation to a large latitudinal range, andabsence of the alien genus in the invaded area. The USAand most of the world maintain “dirty lists” of prohibitedplants. Australia and New Zealand maintain a “clean list”of plants that are allowed to be imported; everything noton the list is prohibited(17). These two countries require astrict protocol for importing prohibited plants for researchand possible development into commercial crops. In ei-ther approach, knowledge of what makes a plant a weedhelps in formulating quarantine lists(17). Every noxiousweed kept out of Hawaii means economic losses and en-vironmental damage avoided and a great deal of moneyand effort not required to deal with that weed.

BiocontrolWeed biocontrol is the suppression of weeds by insectsand microorganisms that feed on the target plants or oth-erwise parasitize them. Hawaii has been a pioneer inclassical biocontrol of weeds; i.e., biocontrol in whichthe biocontrol agent is able to sustain itself after releaseinto the environment. The Board of Agriculture andForestry began biocontrol work in the early 1900s. Earlysuccesses against lantana and prickly pear cactus andmore recent success with Hamakua pamakani and Mauipamakani resulted from these efforts(38) (see AppendixII for botanical names of weeds of Hawaii). While suc-cessful biocontrol is extremely economical, success isnot assured. Efforts on gorse, faya tree, christmasberry,and others have not been fruitful so far. Furthermore,success may not be complete. Lantana is still a seriousproblem over large areas. In addition, because biocontrolis species-specific and there are a couple of hundredserious weed species and only limited resources to do

the exploratory, safety, and efficacy research, biocontrolhas to focus on only a few of the most serious weeds.Recently there has been interest in mycoherbicides,pathogenic fungi that are sprayed onto weeds, but incontrast to classical biocontrol, these fungi are unableto persist in the environment and die out with the weed.

Cultural controlCultural control includes those management practicesthat modify the agroecosystem to make the pasture, crop,or forest ecosystem resistant to weed establishment and,at the same time, support overall economic goals. Ex-amples include fertilizing pastures to provide not onlygreater yields but also quicker and denser ground cover;managing livestock using intensive grazing managementsystems(101) in which pastures are intensively grazed forshort periods, allowing grazing to refresh the forage andtrampling to suppress the weeds, followed by a longerrest period for grass recovery; and integrating sheep orgoats to browse brush species and fowl to graze herbsand grasses(90). Some reasonably call the use of livestockin weed management biocontrol, but the difference isthat livestock husbandry is a form of production agri-culture, whereas the use of invertebrates or microbes isa specific weed management tactic.

Mechanical or manual controlPrior to the development of modern herbicides, ranchand forest managers relied mainly on mechanical meth-ods of weed control, such as grubbing, bulldozing, drag-ging, cabling, and mowing. Ranchers used to pull weedsout of the ground with tractors or grub them out withhand tools. These methods were expensive, injurious toforage species, and ineffective over the long term. Heavyequipment exposed the soil to erosion and brought largerocks to the surface, which thereafter hindered mobilityof horses and equipment. Another serious drawback ofmechanical methods of weed control was that they werelabor-intensive and therefore slow. Ranchers did not haveenough slack periods to divert sufficient manpower tocontrol all the weeds on the ranch in a timely manner.The demands of other tasks, equipment breakdowns,rains, and soggy grounds often precluded operations onparts of the ranch. Steep terrain or rocky ground alsohindered weed control operations. Weed control deferredresulted in a more difficult task later.

The most serious aspect of mechanical control is itshazards. Agriculture is a very dangerous occupation,recording 50 deaths per 100,000 workers per year against11 per 100,000 per year for all industries combined(70).In 1993, there were 130,000 agricultural work-related

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injuries and 1100 deaths(27). Tractor rollovers are espe-cially dangerous, accounting for 15–25 percent of farmdeaths. Although the data do not so specify, some ofthese accidents and deaths undoubtedly occurred dur-ing weed control operations. Because mechanical con-trol suppresses weed growth only for short periods, fre-quent retreatments are required, increasing worker con-tact with dangerous equipment.

Weeds germinate from an inexhaustible seed sup-ply in the soil, or they resprout from stumps, roots, orstem fragments. In high-rainfall areas, new flushes fromcut stumps of some species can grow 3–4 ft tall in 3months. Mechanical methods are often used in pasturesand forests, primarily where the weeds, especially woodyor other large plants, must be cleared immediately ei-ther for aesthetics or safety, or as a pretreatment to her-bicide applications.

HerbicidesCompared to mechanical weed control methods, herbi-cides provide greater efficacy at lower cost. Properlymanaged, herbicides provide relatively long term weedcontrol. Spraying equipment is generally cheaper topurchase and operate than the heavy equipment used inmechanical weed control. Chemical weed control ismuch more rapid and provides longer term weed sup-pression than mechanical methods. Furthermore, herbi-cidal weed control results in greater grass production inpastures than does clipping of weeds(18). Chemical meth-ods reduce labor costs, provide greater flexibility in themanagement of labor and, most importantly, reduce therisk of accidents by reducing fatigue and worker expo-sure to power equipment and sharp implements.

For large tracts of land, aerial applications can beextremely cost-efficient, with costs per unit area as muchas a tenth the cost of ground applications. Aerial appli-cations can cover hundreds of acres per day, versus 5–75 acres per day with ground equipment. Moreover,aerial applications can be made on rough terrain andsoggy soils where ground rigs cannot operate.

It is commonly perceived that a single herbicide ap-plication can solve any weed problem and that herbicidesare extremely toxic. Neither is true. Properly used, herbi-cides can reduce weed populations quickly and selectively,and thereby provide immediate increases in grass pro-duction in pastures or native plant growth in forests. How-ever, even under the best of circumstances, herbicideswill not eradicate widely established weeds. Herbicidesoffer suppression of weed populations quickly and forlonger periods than mechanical control methods.

However, herbicides alone are not the answer to

weed problems. Indeed, effective weed management canseldom be achieved by a single method or action. Her-bicides provide a means to suppress or even eliminatestanding weeds. However, it cannot prevent re-infesta-tion except by repeated application, unless managementpractices (e.g., fertilizer application, grazing) or ecologi-cal conditions are changed (e.g., biological control, es-tablishment of a canopy of desirable plants, exclusionof ungulates) to exert more pressure on the weed popu-lation. Herbicides are a management tool, effective andsafe if used properly.

Herbicide hazards in perspectiveThere is a great deal of concern about the health hazardsof pesticides, including herbicides, that is a source ofneedless anxiety. To be sure, some pesticides are ex-tremely toxic (acute toxicity) and do require commen-surately extreme precautions in their handling and man-agement, as is required with any toxic substance. Fortu-nately, most herbicides are not highly toxic, and mostserious cases of poisoning have been the result of thevictims swallowing one of the more toxic chemicalsrather than from unavoidable exposure during normaluse or through consumption of foods derived fromtreated crops. As in all occupations, constant educationand training are required to reduce exposure to hazardsand to deal with emergencies.

Perhaps the greater perceived threat in the publicmind is that pesticide residues in food, air, and waterincrease the risk of diseases, especially cancer (chronictoxicity). The source of this concern, however, is ani-mal tests in which massive doses are administered tosusceptible animals. Using assumptions that greatly ex-aggerate human susceptibility and exposure to pesticides,these data are then converted to lifetime risks to humans.These assessments are often misunderstood as represent-ing predictions or even realized casualties. Confusion iscompounded by the language of risk assessment, inwhich risks are expressed as numbers of human illnessespesticides will supposedly cause.

Toxicologists are almost unanimous in the view thatanimal tests are inappropriate for determining actual risksto humans(2, 4, 85, 99, 116). After 60 years of pesticide use,during the first decades of which regulations were notas stringent as they currently are, age-adjusted cancerrates have not changed, except for lung cancer, whichhas soared, and stomach cancer, which has declined(29).Research(30) reviewing human epidemiological studieshas concluded that pesticides are “unimportant” as acause of cancer; that the real causes of cancer were morea matter of lifestyle (diet, smoking, exposure to sun-

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light) than environmental pollutants.In the USA the average life span, an indicator of

public health, has been steadily increasing in the face ofwidespread pesticide use, to the point that the averagenow approaches the maximum human life span. Fur-thermore, dozens of naturally occurring chemicals infoods (e.g., vitamin A), including fruits and vegetables,were carcinogenic in laboratory tests, and these addedup to 10,000 times the amount of pesticides residues infoods(4, 104). Even that may be underestimated by a factorof 10(105). At current levels of synthetic chemical resi-dues, one would consume only 0.1 oz of synthetic chemi-cal residues from foods in an 80-year lifetime(3, 37) andanother 0.1 oz from drinking water(9). Not all of theseresidues would be pesticides or laboratory carcinogens.In the same lifetime, one would consume 97 lb of natu-ral carcinogens. Evidence also indicates that fruits andvegetables in diets, despite their natural carcinogeniccomponents, actually prevent cancer(30) because they alsocontain high levels of anticarcinogens(2). Thus pesticidemisinformation and scares cause more harm than goodif they cause people to avoid fruits and vegetables forfear of the pesticide residues they may contain. Ratherthan poisoning our food, pesticides have helped to pro-vide the most bountiful and wholesome food supply inhistory. In light of the available evidence, the prudentcourse recommended by health scientists is not to dis-avow use of pesticides but to use them appropriately.

Methods of herbicide applicationTo attain the most economical and effective chemicalweed control with minimal untoward environmental ef-fects, herbicides must be properly managed, not appliedhaphazardly to the weeds. Based on the weeds to becontrolled and the particular situation at hand, the usermust determine the method of application, the herbi-cide, rate, and time of application. There are severalmethods of herbicide application, each with its own par-ticular advantages and utility.

Conventional foliar methodsThe most common herbicide application method is fo-liar application by spraying (Figure 1). It is the easiestand most economical method of applying herbicides.Herbicides can be applied with knapsack sprayers, powerequipment, or by aircraft. In addition, recent innovationshave made possible very-low-volume and ultra-low-volume applications and wipe-on systems.

Choice of herbicideThe user should choose, from among the herbicides reg-istered for the intended use, the herbicide best suited tothe particular goals of efficacy, economy, and environ-mental protection. Obviously, the herbicide must be ef-fective on the target weeds. Certain weeds are more sen-sitive to one herbicide than to another or even to anotherformulation of the same herbicide. For example, 2,4-D

Figure 1. Foliar application of herbicide. Coverage of the entire canopy, not drenching, is critical.

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is effective on many herbaceous broadleaves but is weakon most woody plants. Legumes (Fabaceae) such ascatsclaw and hilahila and composites (Asteraceae) suchas tropic ageratum and ragweed parthenium are gener-ally very susceptible to picloram, triclopyr, and clo-pyralid, while the mustards (Brassicaceae) are tolerantof these herbicides. The polygonaceous weeds (spineyemex, kamole) are extremely sensitive to dicamba. Mostbroadleaves are more sensitive to 2,4-D ester than to theamine salt formulation.

Typically, a given weed species will be susceptibleto more than one herbicide. Other things being equal,the lower-cost herbicide should be used. However, indetermining the cost, the cost per acre, and not the costper gallon, should be considered. For example, catsclawcan be controlled with 0.2 lb picloram active/acre. There-fore, one gallon of picloram (2 lb/gal) is sufficient totreat 10 acres of catsclaw. Even though picloram maycost $100 per gallon, it would be cheaper than a herbi-cide costing $50 per gallon that can treat only 2 acres ofcatsclaw ($10/acre vs. $25/acre).

Other considerations also affect the choice of herbi-cide. Continued use of a single herbicide over time canresult in shifts of weed populations toward species thatare naturally tolerant of that herbicide. Also, weed spe-cies initially susceptible to a herbicide may develop re-sistance to that herbicide if it is used repeatedly overtime. Resistance usually takes many years to develop,but sulfonylureas (e.g., metsulfuron) and imidazolinones(e.g., imazapyr) have triggered resistance in certainweeds in as few as four years. Over-reliance on any her-bicide in these two families will result in resistance toall herbicides in both families(52, 65, 92). Rotation of meth-ods of weed control and herbicides will help to preventweed population shifts and buildup of resistance.

To prevent contamination of groundwater and sur-face water bodies, the applicator should avoid or reducethe use of persistent, soil-mobile herbicides in high-rain-fall areas.

Herbicide selectivityHerbicides are “selective” if they kill or injure certainplants but not others, e.g., dicots (broadleaf plants) butnot monocots (such as grasses). Herbicides are “nonse-lective” if they kill or injure all plants to which they areapplied. Selectivity allows the convenience of broad-cast applications. However, herbicides effective againstbroadleaf weeds also kill desirable legumes. Heavy graz-ing to defoliate forage legumes before spraying, or us-ing a different formulation (e.g., 2,4-D amine instead ofester), may allow the legumes to escape serious injury.

Spot spraying or other directed application proceduresmay also protect forage legumes. There are a number ofgrasskillers (e.g., fluazifop) that can be used where di-cots need to be protected.

Herbicide persistenceHerbicides that are readily detoxified in the soil are “non-persistent” and those that resist breakdown are “persis-tent.” Persistent herbicides provide long-term weed con-trol. However, if legumes in pastures or natives plantsin forests are to be planted into an area after herbicidetreatment, persistent herbicides may injure seedlings ofsuch plants. Thus the choice of a herbicide may dependon the need for longer-term suppression on the one handand the residual toxicity to desirable plants on the other.

Herbicide formulationsSome herbicides are available in hydrophilic (water lov-ing or water soluble) or lipophilic (oil loving or oilsoluble) formulations; 2,4-D and triclopyr are availablein both types of formulation. Commonly, the hydrophilicformulations are amine salts and the lipophilic formula-tions are emulsifiable esters. Both types of formulationmay be applied with water. The amine salts form truesolutions with water, and the esters form an emulsion.The solution is clear, the emulsion is milky. The emul-sion, micro-droplets of oily substance suspended inwater, must be agitated occasionally to keep the herbi-cide formulation and water from separating in the tank.In general, esters are more effective than salts becausethe oily nature of esters allows them to adhere to andpenetrate the waxy cuticle of leaves better than salts.Esters therefore are better in situations where rain islikely to occur shortly after the herbicide application,because they enter the plant quickly and resist beingwashed off the leaves by rain.

Esters are more volatile than amine formulations.Esters can volatilize from the spray droplets and fromthe plant and soil surfaces. The volatilized herbicide canthen be carried with air movement to injure sensitivecrops and other nontarget plants downwind. This is called“vapor drift,” in contrast to “spray drift,” which is themovement of the spray droplets or solid particles. Mod-ern ester formulations are “low volatile” but may stilldrift if improperly managed (e.g., applied with a mistblower). Where wind direction is unfavorable, tempera-ture is likely to be high, and sensitive plants are near, itwould be safer to use a non-volatile product. Volatiliza-tion of esters can also reduce herbicide efficacy on hotdays by reducing the effective rate(22, 100). For basal barkapplications (to be discussed later), oil-soluble formu-

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lations are essential to the efficacy of the method.

SurfactantsSurfactants, a coined term for “surface-active agents,”are chemicals that change the physical properties of liq-uid surfaces. Surfactants, depending on the chemical orblend of chemicals used, can act to enhance emulsifica-tion, dispersal, wetting, spreading, sticking, and leaf-penetration of the solution(8). Although soap and house-hold detergents are surfactants, they are not very effec-tive as agricultural surfactants and should not be usedfor that purpose. Surfactants aid the performance of her-bicides by• improving wetting of the weed; “wetting agents” or

“spreaders” enhance the spread of the spray dropletsand increase the area of contact between the dropletsand the leaf surface and, therefore, penetration of theleaf surface

• increasing resistance of the spray deposit to washingby rain (stickers); the longer the contact between theherbicide and the plant surface, the greater the amountof herbicide absorbed

• reducing the rate of drying of the spray deposit (hu-mectants); dry herbicides will not penetrate the leafsurface

• reducing the proportion of very fine droplets, thusreducing spray drift (drift retardants or thickeners)

• allowing the suspension of insoluble pesticides, i.e.,wettable powders, in water (emulsifiers).

Although reduction of surface tension of the spraydroplets is very important in increasing the efficacy ofherbicides, it is not the only means by which surfactantswork(97). Efficacy increases at surfactant concentrationsbeyond that which provides minimum surface tension(55),suggesting other mechanisms are at work. Surfactantsmay not be necessary when the plant is succulent, butthey can help with mature plants with hardened cu-ticles(59). The effects of surfactants vary. They generallyincrease uptake of herbicides and may increasetranlsocation but may sometimes decrease translocationby causing too severe injury to the target plant(15, 35, 84).

Rates of applicationHerbicide users should apply the recommended rate.Herbicide labels usually state the recommended rate interms of both amount of product and of “active ingredi-ent (a.i.)” or “acid equivalent (a.e.)” per acre. “Acidequivalent” is preferred for herbicides that are acids inthe parent form. “Active” is used in this publication tocover either of these terms, whichever is appropriate.

Overdosing is a common error as appliers, trying to get“better” or “quicker” or “once and for all” kill, may in-crease the herbicide concentration or the spray volumerate, or both. The result is unnecessary expense, unnec-essary release of herbicide into the environment, and,ironically, poor weed control.

Effective weed kill with systemic foliar herbicidesdepends on the herbicide being translocated from theleaves via the phloem into the stem and roots. Too higha rate will shut down the phloem too soon, before theherbicide can be translocated to sites of action(39, 51, 60, 62,

89). Even though treated woody plants might be quicklyand completely defoliated, they would recover quickly(12,

24, 86, 106). A rapid burning or defoliation may be spectacu-lar, but the effect is short-lived. Over the longer term,overdosing often results in much less kill of the weedpopulation than would the optimal, recommended rate.Foliar-applied systemic herbicides should cause a slowdecline of the target weed. The problem should be ap-proached as a long-term one requiring repeat annual orsemi-annual treatments at optimum rates until the weedpopulation is negligible. Thereafter, maintenance treat-ments with low rates of herbicide while the weeds aresmall are much more effective and efficient than wait-ing for the weeds to become a problem again.

CoverageThe importance of good coverage of the target plant withthe spray material cannot be overemphasized. Herbicidesin plants move readily longitudinally but very poorlyradially (horizontally). Thus, unless the herbicide is welldistributed over the plant canopy, control will be poor(31).Treating one side of the weed will result in injury to thatside only. Whether the herbicide is applied at a sprayvolume rate of 5 gal/acre or 80 gal/acre, good coverageis essential(88). Wetting per se is not important; it is onlya means to achieve good coverage. (This principle shouldnot be confused with the need of the spray material onthe foliage having to remain wet in order for the herbi-cide to penetrate the leaf cuticle[98].)

Spray volume ratesFor maximum efficiency as well as efficacy, spray vol-ume rates (spray volume per acre) must be kept as lowas possible while still allowing adequate coverage(58, 68,

103). Water is merely a diluent to make the herbicide sprayvolume large enough to make uniform distribution pos-sible. Any water beyond the minimum volume neededunnecessarily increases work by requiring more volumeto be sprayed and, thereby, more reloadings per acretreated. Fuel consumption and wear of equipment are

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unnecessarily increased. Efficacy is also reduced be-cause, at any given herbicide rate, dilute sprays are lesseffective than more concentrated sprays(1, 33, 67, 72, 94). Forthese reasons it is essential that herbicides be appliedprecisely.

Excessively high-volume application is usually theresult of• drenching by the applicator hoping to get better or

quicker weed kill• use of high pressure either to achieve drenching or

increase the reach (or “throw”) of the spray• a malfuctioning pressure regulator• dense brush that slows the speed of the sprayer.

TimelinessTimeliness of herbicide applications is critical to theeffectiveness of the herbicide and to the efficiency ofthe operation. Herbicide applications should be madewhen the weeds are most susceptible and when envi-ronmental conditions are suitable for effective and safeapplication. Herbicides should be applied under the fol-lowing conditions.

1. When energy reserves in the weeds are low(53).This is usually after plants have expended stored energyto fuel new growth, such as after a drought, after winter(at higher, colder elevations), after a fire, or after previ-ous herbicidal or mechanical treatments.

2. When there are some fully expanded, “soft”leaves(12, 31, 93). At this stage, the cuticle is thin, the leafarea is large enough to retain sufficient amounts of theherbicide spray, and, within the plant, downward trans-location is active as the weed begins to rebuild energyreserves (carbohydrates).

3. When the weeds are young. Small, young plantsare easier to control than larger, more mature, or woodierplants(64, 107, 112). Attacking weeds early in the infestationrequires less herbicide and fewer repeat treatments, af-fords greater mobility, and results in less weed competi-tion. In contrast, allowing weeds to grow too large com-plicates the weed control operation. Equipment move-ment is hindered by large, dense brush, particularly inrough terrain where unobstructed vision is critical. Re-duced speed tends to increase the spray-volume rate,because the sprayer output remains the same while theapplication speed is reduced. The greater mass of foli-age to be treated also means a higher spray volume ratemust be used to achieve complete coverage. Further-more, directing sprays upward to control tall plants in-creases the risk of herbicide drift. Timely retreatment,while the weeds are small, reduces the amount of herbi-cide needed in those subsequent treatments(57, 75).

4. When the weeds are actively growing. Weedsshould be sprayed when they are actively growing andphotosynthesizing. Actively growing plants have leavesthat are succulent and readily penetrable by herbicides.Foliar-applied herbicides must be translocated via thephloem out of the leaves and into storage sites in thestems and roots or to the growing points that need thecarbohydrates (photosynthate). Translocation in thephloem is “powered” by photosynthesis. Active photo-synthesis results in high photosynthate production in theleaves and active translocation of photosynthate via thephloem. Phloem-mobile herbicide absorbed by the leavesmoves with the flow of photosynthate. If photosynthe-sis is active, the flow of photosynthate and phloem-mobile herbicide is strong(11). If photosynthesis is weak,when the plant is diseased(111), for example, or while itis drought-stressed(14, 72), photosynthesis is weak and theflow of photosynthate and phloem-mobile herbicidedecreases or stops.

5. When it is not raining but soil moisture is ad-equate. Maximum uptake of herbicide from the leaf sur-face into the leaf is influenced by rain. Rainfall too soonafter application may wash the herbicide off the leaf sur-face(20, 23, 42, 117). The duration of the rain-free period re-quired for maximum efficacy depends on the weed spe-cies(97), the herbicide(97), the surfactant(16, 84), the herbi-cide formulation(23), the rate of application(25, 117), andenvironmental conditions(35). On the other hand, spray-ing should be done when the moisture status of the soilis adequate for vigorous growth. Furthermore, herbicideuptake is facilitated by succulence of the leaves(12, 93, 107,

112). In hot, dry weather, leaves have a waxier leaf cu-ticle not readily penetrable by herbicides.

Integrated treatmentsTypically, woody plant populations cannot be eliminatedby a single spray application. Most woody species havesufficient food reserves that allow them eventually tooutgrow the effects of a single herbicide spray applica-tion. Thus, repeated or integrated treatments that stressthe weeds over a longer period of time are usually re-quired for effective control, particularly for older, moreestablished infestations. For example, two herbicidesprayings a year apart virtually eliminated guava fromexperimental plots, whereas a single application resultedin the eventual recovery of the weed (44). Similar re-sults were reported for Rubus spp. (6, 7), gorse (13, 69),and lantana (40).

Likewise, burning or mechanical control methodsthat remove most of the plant biomass, followed by aherbicide application early in its recovery, also results

10


in higher weed mortality than a herbicide spraying ofundisturbed plants(56, 69). Topping of woody plants reducestheir biomass, forces the plant to tap its food reserves tofuel regrowth, allows better herbicide coverage to beachieved, and provides more succulent leaves, whichare more readily penetrated by herbicides. This strategyhas been used effectively on lantana(26, 48), Rubusfruiticosis (no common name)(6), gorse(54), and onSolanum auriculatum (no common name) and turkeyberry, species closely related to apple-of-Sodom(100).Tropical soda apple (Solanum viarum) required a mow-ing followed by triclopyr applications for adequate con-trol(71).

In spraying previously treated plants, the succeed-ing treatment should not be done too early or too late.When the plant is in early flushing, translocation of car-bohydrates upward from the roots to the new flush willprevent the downward translocation of foliar-appliedherbicide. Applications should be made when a suffi-cient number of new leaves have fully expanded. Thisis when photosynthesis is active and translocation ofphotosynthate from the leaves is active as the injuredplant rebuilds its energy reserves. Waiting too long al-lows the weed to rebuild its energy reserves.

Climate can be exploited in chemical weed con-trol(53). In leeward areas subject to seasonal drought, her-bicides should be applied early in the rainy season. Atthis time, energy reserves in plants are low after beingtapped to support the new flush after the drought, leafarea is large, and leaves are succulent. After treatmentwith a selective herbicide, the plants would be defoli-ated during the wet growing season and would not beable to rebuild their energy reserves before the onset ofthe next dry season. In the meantime, growth of tolerantspecies would be unhindered by competition from theweedy plants, and soil moisture would be conserved. Inthe higher elevations with more uniform rainfall distri-bution, there is a surge in growth in the spring whentemperatures get warmer. This would be the best time toapply herbicides. However, brush in high-rainfall areastends to exhibit better recovery without the added stressof seasonal drought.

Kona rancher Allen Wall reported that slashingguava in the cool season and spraying the regrowth inearly summer (rainy season) before the weed can regainits vigor effectively controlled this weed of humid ar-eas. This strategy integrates climate with mechanical andchemical control methods.

Drift preventionHerbicides that drift from the target area do not contrib-

ute to weed control. More seriously, such herbicides cancause severe damage to nearby crops or other valuableplants. It is the legal responsibility of the applier to pre-vent herbicide drift. There are six principal factors thatincrease the risk of herbicide drift.

1. Proximity to sensitive plants. The first precau-tion in applying herbicides is to be aware of the locationof sensitive and valued non-target plants. The appliercan then make adjustments in the weed control programto avoid drift hazards too close to non-target plants.

2. Droplet size. Fine droplets have a greater poten-tial to drift than large droplets. High pressure spray andsmall nozzle orifices yield a greater proportion of “fines”than low pressure and large orifices. However, coarsesprays require higher spray volumes than fine spraysfor adequate coverage. The applier therefore must ad-just the spray to fit the conditions.

3. Wind. Herbicides should be applied during stilltimes of day. High winds will displace herbicides. Justhow great a wind velocity can be tolerated depends onthe other factors stated here, but in any case it shouldnot exceed 10 mph, or any wind speed limit stated onthe label.

4. Height of spray. The higher the arc of the spraythe greater the distance spray can drift. Thus, aimingthe spray up toward the canopy of tall brush increasesthe drift potential, particularly when high pressure (finemist) and volatile formulations (esters) are used.

5. Formulation. Long distance drift involves herbi-cide vapor. Ester formulations of herbicides are some-what volatile. Because of the threat of vapor drift, cur-rent ester formulations are manufactured in “low-vola-tile” formulations. However, even these can pose a threatif mismanaged. For example, applying even “low vola-tile” esters with a mist blower would greatly increasevolatilization into the air.

6. Timely weed control. One of the most effectivemeans to prevent drift is to take care of weed problemsearly. Most drift problems occur when treating tall brush.By tackling weeds while they are small, the applier cankeep the nozzles close to the ground, and thus avert theneed to spray upward into the air and the need to usehigh pressure to increase the reach of the sprayer. Also,lower herbicide rates are needed when the weeds aresmall.

Calibration of spray volume rateand herbicide concentrationTo ensure application of the recommended rate of a her-bicide, the applier must determine the spray-volume rate(SVR), i.e., the total amount of material (herbicide plus

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carrier) to be applied per acre (even if less than an acrewill actually be sprayed) because the herbicide rate de-pends on the SVR. To accomplish this, the applier mustcalibrate the sprayer. The simplest calibration procedureis to spray a plot of known area to determine the re-quired volume of water that will provide good cover-age, spraying at a constant, comfortable speed and low(15–45 psi), constant pressure. Thus SVR =

water sprayed (gal) 43560 sq ft

swath width (ft) x distance (ft) acre

Then, herbicide concentration =

recommended herbicide rate

SVR

Example 1. Boom sprayerCheck each nozzle by collecting the output over a set timeand measure the volume. The output of the nozzles shouldnot vary from one another by more than 10 percent.

Assume a boom sprayer with a 20-ft spray width.At a constant speed of 3 miles per hour, the sprayer dis-charges 4.2 gal of water over 300 ft. Thus,

For each acre to be sprayed, the recommended amountof herbicide must be diluted with enough water to makea total of 30 gal spray mixture. Assuming 0.5 gal herbi-cide/acre is recommended, then

herbicide concentration =

0.5 gal herbicide/acre

30 gal spray/acre

Thus the concentration of herbicide required is 1.7%.With this information, any volume of spray mixture canbe prepared.

Example 2. Power sprayer, orchard gun method1. Measure off a known area.2. Record the water level in the sprayer tank.3. Spray the known area uniformly with water as would

be done with the herbicide mix using a low, constantpressure and the same nozzle setting as will be usedin the application. The larger the area sprayed, themore accurate the calibration.

4. Determine the amount of water used by reading the

volume gauge and subtracting that volume from thestarting level.

Assuming a known area of 60 x 200 ft and that wateruse was 22 gal, then

Assuming a recommendation of 0.5 gal herbicide/acre:

herbicide concentration =

0.5 gal

80 gal

Thus the herbicide dilution required is 0.6%.

Example 3: Knapsack sprayer(BASF no-math version [unpublished handout])1. Mark off a calibration plot that is 18.5 ft by 18.5 ft.2. Spray water over the plot and measure the time in

seconds to do it: (example: time = 45 sec).3. At the same constant pressure, by regulator or con-

stant pressure on the handle, spray into a bucket forthe same time and then measure the volume of watercollected in fluid ounces: (example:volume collected= 25 fl oz). The number of fluid ounces collected isequal to the SVR in gal/acre (example: 25 gal/acre).

Assume that the herbicide label recommends 1 qt (0.25gal/acre); then, the concentration of herbicide should be:

0.25 gal/acre

25 gal/acre

Thus the herbicide dilution needed is 1.0%.

Important note: If the spray volume rate turns out to betoo high, repeat the calibration and try to get the sprayvolume rate lower. This can be accomplished by increas-ing the speed of application, reducing the sprayer pres-sure, using nozzles with a smaller orifice, or a combina-tion of these. Boom sprayer volume rates should be about25 gal/acre, orchard gun sprayers 30–80 gal/acre, andknapsack sprayers 20–40 gal/acre, depending on the sizeof the target weeds.

x

SVR =30 gal

acrex

4.2 gal

20 ft x 300 ft

43,560 sq ft

acre=

= 0.017, or 1.7%

SVR =80 gal

acrex

22 gal

60 ft x 200 ft

43,560 sq ft

acre=

= 0.006, or 0.6%

= 0.01, or 1%

12


Drizzle foliar application

Logistics limit conventional sprayingThe greatest cost component in herbicide applicationsis labor, in part because of the large volume of carrier,usually water, that must loaded, transported, mixed, andsprayed. This is particularly difficult in areas that areremote from water sources or only accessible by foot,i.e., areas that must be treated with knapsack sprayers.In addition, conventional spraying is also laborious be-cause knapsack sprayers have short throws, so the ap-plicator must walk up to each weed treated, and becauseof the frequency of re-loading that is necessary. Becauseof this cost and the effort required in conventional spray-ing, weed control operations may not be performed in atimely manner. This allows weeds to grow larger be-tween treatments and become more difficult to control.On the other hand, a highly efficient method fosterstimely weed control and eventually requires less laborand material as weed size and stand density are reduced.The inefficiencies of treating severe weed infestationsare thus avoided.

The drizzle methodA cost- and labor-efficient method of herbicide applica-tion was developed by Shigeo Uyeda (now retired) forthe McBryde Sugar Company, Kauai. Originally calledthe “Magic Wand” method(76), the drizzle method em-ploys an orifice disk (Spraying Systems orifice plate4916-20, 0.020 inch diameter orifice recommended) inplace of an atomizing nozzle and a fine strainer (100–200 mesh) to keep the orifice clear. A fine jet-stream isejected (30 psi suggested pressure) through the orifice(Figure 2a, 2b), which breaks up into large droplets thatdrizzles onto the plants (Figure 2c). The large, sparselydistributed droplets are contrary to the widely acceptedconcept of an optimal droplet deposition pattern, i.e.,very many, very fine droplets(19, 67). Nevertheless, thedrizzle method has proved sufficiently effective and veryefficient(73, 75, 76, 77, 79, 80). Broadcast application is achievedby waving the wand over the target area. Precise spotapplication is achieved by aiming the wand at the targetweed. The drizzle apparatus can also be used in very-low-volume basal bark applications (see Basal barkmethod, below).

Figure 2a. The drizzle method of foliar herbicide application.

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Figure 2c. Droplet distribution of herbicide applied by the drizzle method.

Figure 2b. Close-up of drizzle apparatus nozzle.

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Efficiency of the drizzle methodThe drizzle method is very labor-efficient. The effi-ciency of the method is derived from its very-low-vol-ume (VLV) application rate (1.6 gal/acre) and a throwof 15 ft. Only small quantities of water have to be loaded,transported, mixed with herbicide, and applied. Down-time is greatly reduced, as relatively few re-loadingsare required. The reach of the drizzle applicator meansthe applier does not have to walk up to each weed aswith conventional knapsack spraying. In open pastures,the user walking at 1 ft/sec and waving the wand in ahorizontal arc to cover a swath 20 ft wide can broad-cast-treat 1 acre in 36 minutes at the application vol-ume rate of 1.6 gal/acre. On trails, the applier with aconventional knapsack sprayer must treat each side ofthe trail in turn. The drizzle applier can treat both sidesof the trail in one pass. A trail 7 ft wide can be treated at2 mph. On Koaie Trail on Kauai, where clearing 3 milesof trail would have been required 576 worker-hours formanual clearing or 40 worker-hours for conventionalspraying, only 4.5 worker hours were required usingthe drizzle method,(75, 79) and weed suppression was ex-cellent. The greater manpower requirement of conven-tional spraying results from the higher volume rate thatwould have required more porters to carry water. Thiswould be exacerbated on trails with few or no watersources. Koaie Trail frequently descended to KoaieStream. The disparity in cost between conventionalspraying and drizzle application would have been evengreater where water must be transported over the entiretrail, expecially where the trail is rough and steep. Theexperience of Koaie Trail has been repeated on severalother trails on Kauai where mechanical control meth-ods have been replaced by drizzle applications of her-bicides and labor requirements have been reduced by83–98%(73, 75).

Other advantagesIn addition to labor efficiency, the drizzle method offersseveral other advantages:• Low drift potential—because of the large droplets,

drift is minimal.• Safety—heavy loads are a risk factor in injuries. Fur-

thermore, that risk is compounded by fatigue causedby carrying such heavy loads. This is especially so inrough and steep terrain. Very-low-volume methodsreduce the weight and number of loads that appliersand porters must carry. The applier can cover morethan an acre with a half-full knapsack.

• Reliability—unlike other more complex very-low-volume equipment, the drizzle method is not subject

to breakdowns because it employs ordinary sprayers.• Cost and convenience—any ordinary knapsack

sprayer can be easily and cheaply converted into adrizzle unit and back again. In addition, tank pres-sure is easier to maintain with a manual knapsacksprayer in a drizzle mode because of the very lowoutput. The drizzle unit is easily deployed, in con-trast to heavy power sprayers or crews of laborers formechanical control. One person on a moment’s no-tice can go off to treat a large area. The convenienceof the drizzle method encourages more timely weedcontrol. The resulting lower weed biomass makessucceeding operations easier and with less herbiciderequired.

• Versatility—the wand of the drizzle unit can be wavedto broadcast herbicides, aimed for a very precise spotapplication and, with a crop oil carrier (see below),used for basal bark treatments. With its reach of 15 ft,it can be used on brambles, weeds to 12 ft tall, andplants over the edge of cliff-side trails.

• Affordability of oil carriers—because of the very lowvolume of the drizzle method, crop oil carriers areaffordable: only 1.3 gal/acre or less is required inbroadcast applications. Ester formulations of triclopyrcan be applied in a crop oil carrier to treat weeds tol-erant of foliar applications of triclopyr in water, suchas Mauritius hemp and gorse. Triclopyr in crop oilcan also be used in very-low-volume basal bark orstump treatments of susceptible woody species (SeeBasal bark method, below).

Limitations of the drizzle methodFor certain weeds, the drizzle method is not as effectiveas conventional spraying. In addition, the user is lim-ited to liquid herbicides (solutions or emulsions) withlabels that allow a high enough concentration to applyan effective amount at a very low spray-volume rate.Wettable powders will clog the strainer or the fine ori-fice of the disk. There are only a handful of herbicidesthat are appropriate for drizzle application (Table 1).

CalibrationAs in any method of application, calibration is criticalto delivering the correct volume and, thereby, the de-sired herbicide rate. This ensures efficiency, efficacy,economy, and environmental protection. The most con-venient set-up is to use an orifice disk with a 0.02 inchorifice at a tank pressure of 30 psi. With a manual knap-sack sprayer lacking a pressure regulator, constant pres-sure can be achieved by maintaining constant pressureon the handle. This will be easy to do because the out-

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put is so low that the tank pressure declines very slowly.It really does not matter what pressure is used as long asit is not so high as to atomize the output nor too low tomaintain maximum throw. Of course, constant pressureshould be maintained not only during calibration but alsoduring the actual application. (To observe the dropletdistribution pattern, drizzle a dry paved area, walking at1 ft per second and covering a swath 20 ft wide). Thecalibration method described here assumes a spray swathof 20 ft, an application speed of 1 ft/sec, and an SVR of1.6 gal/acre. Application speed can then be adjusted fornarrower swaths, e.g., increasing the speed three-foldfor spray swaths of one-third the original calibrated spraywidth (20 ft). However, to treat very narrow swaths, e.g.,a 2-ft swath along a fence line, increasing applicationspeed sufficiently will not be practical, so a smaller ori-fice disk must be used to provide a lower output andsmaller droplets, or the herbicide concentration must bediluted and the SVR increased to obtain the desired her-bicide rate.

To calibrate a drizzle unit:1. Measure the water output of the drizzle sprayer by

collecting the discharge for 1 minute at constant pres-sure. (Because of the low volume, the collected wa-

ter is best measured in milliliters (ml) with a metricgraduated cylinder, or the collection period can beincreased to several minutes until a volume measur-able in a metric measuring cup is collected):

Volume collected (ml/min)

60 sec/min

2. Divide output by 3785 (ml/gal) to convert output togal/sec:

Output (ml/sec)

3785 ml/gal

3. A swath 20 ft wide and 2178 ft long covers one acre.At a walking speed of 1 ft/sec, it would take 2178 secto treat 1 acre.

43560 sq ft/acre

20 sq ft/sec

4. Multiply (2) by (3) to get the spray volume rate ingal/acre:

Output (gal/sec) x 2178 sec/acre = SVR (gal/acre)

Table 1. Herbicides for drizzle application.(Always check labels before use, as they are subject to revision).

Method Concentration4

Product Herbicide Site1 Use2 of application3 (%)

Banvel® dicamba P, F, N B f 15

Garlon® 3A triclopyr amine P, F, N B f 20

Garlon® 4 triclopyr ester P, F, N B f, bb 20

Hi-Dep® 2,4-D amine*5 P, F, N B f 15

MCP Amine® MCPA P, F, N B f 15

Pathfinder® II triclopyr ester P, F, N B bb 100

Redeem® triclopyr amine P B f 20

Remedy® triclopyr ester P B f, bb 15

Rodeo® glyphosate5 A, N NS f 15

Roundup® glyphosate5 P, F, N NS f 20

Velpar® L hexazinone P, F, N NS f, s 67

*Restricted.1A = aquatic, P = pasture, F = forest, N = noncropland. Check label for specific uses.2B = broadleaves or dicots, NS = nonselective.3f = Foliar, bb = basal bark, s = soil.4Suggested concentration based on 1.6 gpa application volume rate. If allowed, higher concentrations may be used. Otherwise, higherherbicide rate requires higher application volume rate, e.g., 3.0 gal/acre or higher. Lower concentrations are sufficient for more susceptiblespecies and for seedlings.5Many brands of 2,4-D and glyphosate are available. Check label for site uses and allowed concentrations. 2,4-D sold in quantities of a quartor less is not restricted.

= Output (ml/sec)

= 2178 sec/acre

= Output (gal/sec)

16


Alternatively, the equations above can be summarizedto calculate the SVR for applicaations 20 ft wide and anapplication speed of 1 ft/sec:

Output (ml/min) x 0.0096 = SVR (gal/acre)

5. Determine the concentration of herbicide by dividingthe recommended herbicide rate by (4), the SVR:

0.25 gal herbicide/acre (example rate)

1.5 gal/acre (example SVR)

6. Determine the speed to treat narrower swaths, suchas a trail, from Step 4. Treating a narrower swath thanthe 20-ft one calculated in Steps 1–4, for example, 7ft, requires a greater application speed to maintainthe same SVR:

20 ft

7 ft

Drizzle foliar application, water carrierHerbicides soluble or miscible in water can be drizzledover weeds at the appropriate concentration. In broad-cast applications, the wand should be aimed over thetarget plants and waved to achieve uniform distribution.The wand can be waved in a circular motion or loopedin mid-swing to avoid underdosing the middle and over-dosing the edges of the swath as the wand slows at theends of the swing before its direction is reversed. Thebasic principles of herbicide application apply to drizzleapplication as they do to conventional spray applica-tions. There should be uniform distribution of the drop-lets over the whole canopy of the target weed withoutoverdosing. Taller weeds are a problem because the leeside of the plant would be underdosed. These can betreated from two opposite sides to ensure complete cov-erage. However, it would probably be more economicalinstead to re-treat in a few months when there is a newflush of growth and with the canopy thinned out by theprevious treatment. After the standing weed populationhas been eliminated, reinfestations should be re-treatedwhen the weeds are small, semi-annually or annuallydepending on the climate. At this time the weeds will bemore susceptible and lower herbicide rates can be used.Thus over time the amount of herbicide required willdiminish. For example, in annual applications on KoaieTrail on Kauai, the second application required only 41percent as much herbicide as the first application, 39percent on the third, and 25 percent on the fourth(75).

Weed species susceptible to drizzle-applied triclopyrinclude highbush blackberry, yellow Himalayan rasp-berry, catsclaw, Formosan koa, bur bush, sacramento bur,melastoma, Indian pluchea, and sourbush. Weeds sus-ceptible to glyphosate are lantana, guineagrass, Jobstears, Californiagrass, palmgrass, fountaingrass, andhuehue haole.

Drizzle foliar application, crop oil carrierCertain weeds that are tolerant of herbicides in watercarrier may succumb to herbicides in an oil carrier. Non-phytotoxic crop oil can be used as a carrier with the esterformulation of triclopyr. The oil, which contains emulsi-fiers to make mixing with water possible, is harmless toplants but helps oil-soluble herbicides penetrate leavesand stems and thereby increases efficacy. Crop oil mayalso be used as an adjuvant at 0.5–20%. When using oilas an adjuvant, the herbicide and oil should be mixedfirst, then added to water and made to volume with morewater. Gorse and Mauritius hemp are examples of weedstolerant of applications of triclopyr ester in water butsusceptible to the same herbicide in a crop oil carrier.

Cut-surface methods

NotchingA very effective albeit labor-intensive way to chemi-cally control brush and trees is to mechanically penetratethe bark and place the herbicide directly into the sap-wood (xylem) of the plant (Figure 3). The herbicide isthen translocated throughout the plant, provided that thetarget plant has actively functioning leaves. Specializedequipment such as tree injectors may be used to piercethe bark and deposit the herbicide. However, a simplemethod requiring no specialized equipment is the “notch-ing” or “hack and squirt” method. In this method, notchesan inch or so deep into the sapwood are made every 4inches around the trunk with an ax or machete. Becauseherbicides do not move radially (horizontally) in the plantvery well, the herbicide must be placed in wounds madeat intervals around the circumference of the trunk. Her-bicides applied to a single notch will translocate verti-cally and likely kill only that vertical segment of theplant. The wound is cut at a 45° angle to form a recep-tacle to retain the herbicide, and the bark is pried awayfrom the trunk to increase the area of herbicide contactwith the sapwood. The notches should be made as closeto the ground as possible to enhance suppression of budsat the root crown,(58, 61) although this is not necessarywith all species(96). A study done in Australia demon-strated that herbicide applications to wounds made by

= 0.17, or 17%

1 ft/sec x = 2.86 ft/sec, or 3 ft/sec

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puncturing the trunk with a narrow bladed instrumentgave better kill than did slashing it with a machete(95).This was attributed to better penetration into the sap-wood by the narrow blade. Although the machete causeda longer cut, only a short section of the blade actuallyreached deep into the sapwood. Also, the narrow-bladewound probably retained more herbicide. Herbicidestended to run out of the edges of machete cuts. In treesthat fork close to the ground, it would also be a goodidea to notch each branch on the inside of the crotch toimprove distribution of the herbicide within the aerialportion of the tree.

Notching is very effective on dicot species that haveone or a few trunks, provided a suitable herbicide is avail-able. Obviously, this method would be difficult on shrubswith many fine stems. Trees of 8-inch trunk diametercan be treated at a rate of 21 per worker-hour(82, 83). Be-cause each plant is treated individually, there is littlelikelihood of injury to non-target plants.

For species somewhat tolerant of the herbicide used,notches can be made end-to-end in a continuous ringaround the trunk (frilling)(61, 87). This in effect doublesthe applied dose(95). For larger trees, drilling holes intothe trunk allows a higher dose to be applied (Figure 4a,4b). For example, spaced notches treated with dicambaor glyphosate were inadequate to kill large roseappletrees. However, excellent control was obtained with thesame herbicides when 4 ml of either was applied to

drilled holes, 0.5 inch in diameter by 3–4 inches deep.The holes were drilled at a downward angle every 10inches around the base of the trunk(43, 44).

The best herbicide to use in notching depends onthe weed to be treated. Any of the brush-killers could beappropriate. The salt formulations are preferable to theesters because they are translocated more readily, al-though the latter are usually satisfactory(49, 61, 95). In addi-tion to the brushkillers, glyphosate is very effective onseveral species (e.g., fayatree, karakanut, paperbark, androseapple) when applied by the notching method or todrilled holes.

The amount of herbicide that should be applied var-ies with weed species. The recommended rate is usually1 ml per notch or 4 ml per drilled hole of the concen-trated herbicide or of herbicide diluted as much as 20times. At 1 ml of concentrated herbicide per notch, 1 floz of herbicide is sufficient to treat 28 notches. There isno particular advantage to diluting the herbicide, exceptfor economy in those cases where the diluted herbicide ispotent enough to kill the plant. The notches can hold onlya limited volume of herbicide; some of it will leak outfrom the edges of the notch. More concentrated solutionsallow more herbicide to be absorbed into the xylem. How-ever, some herbicide labels dictate the concentrations thatmay be used. Should the label require dilution, mix onlyenough for one day’s needs, because dilution with waterwill accelerate degradation of the herbicide.

Figure 3. Cut-surface (notching) herbicide application. Notches must be made around the stem.

18


Cut-stump methodA variant of the cut-surface treatment, the cut-stumpmethod, is useful in dry areas where there is a need toclear standing vegetation. The plant is cut down andconcentrated herbicide is immediately applied to thesapwood of the stump (Figure 5). It is essential that the

Figure 4b. Applying herbicide into drilled holes.Apply 3–4 ml of herbicide concentrate to each hole, unless otherwise directed by the label.

Figure 4a. Drilling holes to treat a large tree.Holes about 5⁄8 inch diameter by 31⁄2 inches deep must be made at downward angle at12-inch intervals around the trunk.

application be made immediately after cutting, becausethe sap in the sapwood will recede into the stump, draw-ing down the herbicide with it into the region of the rootcrown where shoots originate. Waiting even a few min-utes allows air into the sapwood and blocks the entry ofthe herbicide, much as a vapor lock in a fuel line blocks

19

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the flow of fuel(49). This method may not work in high-rainfall periods because the sap will ooze out of the stumpand keep the herbicide from entering the sapwood(44).

Basal bark methodThe basal bark method is very effective for killing largeshrubs and small trees(28, 58). However, like notching, it islabor-intensive because each plant must be individuallytreated. The high-priced oil carrier also adds to the ex-pense. This combined high cost of material and laborrestricts the utility of the basal bark method to small popu-lations of hard-to-control species or other special situa-tions requiring sure “kill” or protection of nearby non-target plants that would be injured by foliar spray drift.

In the basal bark method, an oil-soluble formula-tion of a suitable herbicide and a light oil are used topenetrate the bark. This solution, 2–8% herbicide in oil,is sprayed or brushed onto the base of the trunk of thetarget plant. The trunk is wetted from about the 20-inchlevel down to the soil line (Figure 6). Effective controlrequires that the entire circumference of the trunk betreated. Misses along the trunk circumference could al-low buds to sprout(36). There should be a little runoff towet the soil around the base of the trunk to ensure thatthe root crown, which is an active zone of bud forma-

tion, is adequately treated. Plants susceptible to basalbark treatments would be even more susceptible to stumpbark treatments with the same oil-herbicide treatment(Figure 7).

The oil used as the carrier should be a light oil suchas diesel, kerosene, or a crop oil made specifically forthis purpose, which is capable of penetrating the essen-tially waterproof bark. Heavy oils such as motor oil orgear oil are not as effective in penetrating the bark, anduse of used motor oil would be illegal. Crop oil, a highlyrefined oil, is less toxic than fuel oils and is nearly odor-less. For basal bark treatments, water is useless as a car-rier because it cannot penetrate the bark.

The herbicides used in basal bark treatments must beoil soluble, either esters or long-chain amine salts.Triclopyr, 2,4-D, and related herbicides are available inester formulations and are thus registered for basal barktreatments, along with some salts, such as imazapyr, thatcan be mixed with oils. Although the effectiveness of 2,4-D against woody plants is limited, there are a few speciesagainst which 2,4-D in basal bark treatments is useful.However, it is very effective on stumps of many species,even though it may not be effective on standing trees ofthe same species. For non-crop and forest uses, imazapyrin oil is an effective basal bark and stump treatment.

Figure 5. Herbicide application to cut-stump surface.Application of herbicide concentrate should be made immediately after felling. Worksbest in dry season.

20


Very-low-volume basal-bark and stumpapplicationsEster formulations of triclopyr may be mixed in oil at20% or more and applied as thin-line or very-low-vol-ume applications to control woody plants (Figure 8) andto kill stumps (Figure 9). Triclopyr ester may also beused as the concentrate in this way. Low-output equip-ment must be used to avoid overdosing. On larger plants,applications should be made at least on two oppositesides of the basal stem. Susceptible species are youngplants with juvenile bark and those species with thin bark,such as strawberry guava, Molluca albizia, gorse,catsclaw, and velvet tree. Downy rosemyrtle, Formosankoa, and melastoma are also susceptible but require ap-plications from two sides. Large trees and species withthick, corky barks cannot be controlled by this method(e.g., paperbark, java plum). Applications to stumps or toresprouting stumps should be very effective (Figure 9).

Figure 7. Stump-bark herbicide application.Apply herbicide-oil solution to the bark completely around thestump. This is usually the most effective method to kill woodyplants.

Figure 6. Basal bark herbicide application.Apply herbicide-oil solution completely around the stump fromground level to 18–24 inches.

Soil-applied herbicidesSome pre- and postemergence herbicides are applied tothe soil and taken up through the roots of target plants.Three granular or pelleted herbicides are registered foruse in Hawaii: dicamba (Veteran® 10-G [BASF]), hex-azinone (Velpar® and Pronone Power Pellets® [DuPont]),and tebuthiuron (Spike® 20P [Dow Agrosciences]).Dicamba and tebuthiuron selectively control broadleafweeds. Hexazinone, also available as a wettable powderand a liquid concentrate, is nonselective but may be ap-plied selectively in spots at the base of plants or in gridpatterns (hot spots) in larger infestations. While grassesare killed at the small application spots, no major dam-age to the grass sward is incurred. The roots of broadleavesthat feed where the hexazinone hot spots are will absorbthe material, which then kills them.

Because of its low animal toxicity and poor mobil-ity in soils, tebuthiuron is an environmentally safe her-

21

UH–CTAHR

Figure 8. Very-low-volume basal bark herbicide application.Apply oil-herbicide solution in horizontal or vertical streaks. Works best on thin-barked species and plantswith juvenile bark.

Figure 9. Very-low-volume herbicide application to stump bark.Apply oil-herbicide solution in streaks around the stump bark.

22


bicide. It is active against guava, koa haole, apple-of-sodom, and christmasberry, although larger plants maybe more tolerant(47, 74). Control of fayatree, Formosan koa,gorse(46, 48), and downy rosemyrtle with tebuthiuron(Univ. Hawaii, unpublished data) has been poor. It isimportant to apply the proper amount of any granularherbicide. The material is expensive, and grass can beinjured by an overdose. Note that with Spike 20P(tebuthiuron), 10 lb/acre is equivalent to only 2 pelletsper square foot.

Dicamba, an excellent foliar herbicide on poly-gonaceous weeds (spiney emex, kamole) and on guava

and other species, has not shown much promise onHawaii’s woody plants in the granular formulation(45, 46).

Hexazinone is a persistent and mobile herbicide thatis of low animal toxicity. It would pose no groundwatercontamination threat when used sparingly, particularlyin drier areas. Because it is nonselective, it should notbe used in broadcast applications over large areas in anycase. Although hexazinone is very effective on mostweeds, the efficacy of it and tebuthiuron have been er-ratic against weeds in small-plot soil applications in for-ests (Univ. Hawaii, unpublished data).

23

UH–CTAHR

This appendix lists and describes some of the herbicidesregistered for weed control in pastures and ranges inHawaii. The primary source of the information on her-bicide properties is the Herbicide Handbook of the WeedScience Society of America, 7th edition(113, 114) and thelist of registered herbicides provided by the PesticidesBranch of the Hawaii Department of Agriculture. Inaddition, some information was obtained from labels andtechnical sheets issued by the manufacturers. Becauseof constant changes in registration and labels, the useris responsible for verifying that the information in thispublication is current.

Explanation of herbicide description

Use“Use” refers to situations and types of weed infestationswhere the herbicide may be useful. “Selectivity” refersto the capability of the herbicide to kill one type of plant,usually the weed, but not another. “Preemergence”means before the newly planted desirable plants or weedsor both emerge from the ground; “postemergence” meansafter these plants are up. Some herbicides may be effec-tive both preemergence and postemergence.

FormulationsHerbicides are of several different types of formulations.Herbicide manufacturers and formulators design theseformulations based on chemical properties, intended use,and customer demands. Some of these formulations are:

Water soluble solids. These powders or crystals canbe dissolved in water for application. The mixture is atrue solution; the solutions are clear.

Water soluble concentrates. These liquid concen-trates, usually salt formulations, can also be dissolvedin water to form true solutions.

Emulsifiable concentrates (EC). These are oil-soluble products that are formulated with emulsifiers sothey can be diluted with water. The resulting emulsionsare not true solutions. The oily herbicide is dispersed asmicro-droplets in the water carrier, forming a milkyemulsion. The emulsion will begin to separate into itswater and oil components if allowed to stand withoutoccasional agitation. Emulsifiable concentrates can be

Appendix 1Herbicides Registered for Use in Pastures

and Natural Areas of Hawaii

dissolved in oil for basal bark applications or to enhancefoliar uptake, if allowed by the label. Herbicides in ECformulations are slightly volatile. They may vaporizefrom spray droplets and plant and soil surfaces, espe-cially in hot weather, and they may injure non-targetplants downwind. However, current formulations are“low-volatile” which means the tendency to volatilizeis greatly reduced compared to the old ester formula-tions. Still, greater precautions must be taken with es-ters than with non-volatile formulations.

Wettable powders. Wettable powders are mixturesof insoluble herbicides in clay and surfactants that canbe mixed with water to form a suspension (solids sus-pended in water). The suspension requires constant agi-tation to prevent settling. For this reason, wettable pow-ders must not be used without an agitator in the tank.Similar formulations are the flowables and dry flowables.The flowable is a pre-slurried form of the wettable pow-der designed for easier handling. The dry flowable ordispersable granule is designed for “dustless” handling.Both also require vigorous agitation during applicationto prevent settling. Wettable powders and its variantscontain 60–90% of the herbicide.

Granules/pellets. Granulated material, exceptdispersable granules, are designed for dry soil applica-tion. Such herbicides must be rather persistent andreadily absorbed by roots. They are applied by hand,mechanical spreaders, blowers, or aircraft. Granules andpellets for direct application to the soil are of low con-centration, 2–20%.

ProductsSome herbicides are manufactured or formulated by sev-eral firms; each has its own brand name. Others, stillprotected by patent, may have only a single manufac-turer but several brand names. Manufacturers may usevariants of a brand name on different formulations ofthe same herbicide and on mixtures in which the herbi-cide is used. For example, Tordon 22 K (DowAgroSciences) contains only picloram, but Tordon 101(Dow AgroSciences) is a mixture of 2,4-D and piclo-ram. The user should be aware of the content of the prod-uct when buying a herbicide. Different brands of thesame herbicide may have different registered uses. The

24


applier cannot assume that different brands, even of thesame herbicide and formulation, can be used in the sameway.

ApplicationListed under this subheading are the approved applica-tion methods of the herbicides under discussion. Beaware that different brands of the same herbicide mayallow different application methods, so the labels of theherbicide being considered for use must be read.

Behavior in plantsPlants absorb herbicides via the foliage, the roots, orboth, depending on the characteristics of the chemical.Most herbicides are systemic, i.e., once absorbed by theplant, they must be translocated to some site where theyaffect the plant. Herbicides travel downward from theleaves to the roots via the phloem and upward from theroots via the xylem (called “sapwood” in woody plants).Some herbicides are restricted to one transport systemor the other, others are immobile, and still others travelmore or less freely in both systems. (Many herbicidesthat are phloem-mobile in foliar application can be ap-plied cut-surface into the xylem). This chemical charac-teristic also influences how herbicides are managed.

The mode of action of herbicides varies. Plant hor-mones cause rapid but abnormal growth, photosyntheticinhibitors shut down photosynthesis, contact herbicidesdisrupt cell membranes and cause plants to dry up, in-hibitors of cell growth and division cause stunting, in-hibitors of respiration cause the plant to use up its storedenergy, and inhibitors of biochemical synthesis causecollapse of the plant. The symptoms produced are cluesto whether the herbicide is working or not and whetherit is the cause of non-target plant injury.

Behavior in soilsTwo characteristics of herbicide behavior in soils areimportant in herbicide management: persistence andmobility. Mobility, in turn, depends on how tightly theherbicide is adsorbed by or adheres to soil particles. Aherbicide resistant to degradation (persistent) will beactive longer both in the soil and in plants. If it is alsomobile, it may cause problems by moving with waterout of the target area and injuring plants in non-targetareas or getting into the groundwater. A non-persistent,mobile herbicide, however, will degrade before it cantravel out of the target area or into groundwater. A per-sistent, immobile herbicide will stay in place until it iseventually degraded.

The “half-life” of a herbicide is the time required to

detoxify half of the herbicide present in an ecosystem;this is the standard measure of persistence. Degradationof pesticides is faster in warm, moist soils and slower incold, dry soils. In general, herbicide leaching is more ofa problem in high-rainfall areas than dry areas and insandy soils than in soils high in clay and organic mattercontent.

ToxicityPesticides must undergo rigid toxicity tests to determinetheir safety. Listed under this heading is the acute oralLD

50 of the herbicide for rats. Although only results on

rats are given, the testing protocol requires various testson fish, birds, dogs, and other animals to develop thetoxicology profile of the herbicide. “LD

50” refers to the

amount of material in mg per kg of bodyweight of thetest animal that is required to kill 50 percent of the samplepopulation. The toxicity rating scale is listed in Table 2,along with some example pesticides and common non-pesticidal products as a frame of reference (note that thehigher the LD

50, the lower the toxicity).

RegulationsPesticides are categorized into two groups for regula-tory purposes: “restricted use” and “unrestricted.” Ap-plication of restricted use chemicals requires that theapplier or the applier’s supervisor be certified to applyrestricted pesticides. The “restricted” category is as-signed to chemicals not only because of hazard to hu-mans and animals but also for potential hazard to non-target plants and contamination of the environment. Pi-cloram, for example, is restricted because of its hazardto non-target plants and to groundwater, but it is of verylow animal toxicity. Unrestricted chemicals may be pur-chased and used by persons without certification. Re-gardless of classification, however, any pesticide usemust be consistent with its label directions.

For a pesticide to be used legally in Hawaii, it mustbe licensed for sale and it must be registered for the in-tended use. Some pesticides and uses may be national;that is, they can be used in all states. Some pesticidesand uses may be restricted to one or more states. Regis-trations are specific for a single brand-name product.Thus a new brand of 2,4-D must be newly registered foruse and sale. Different brands or different formulationsof the same herbicide may have differences in the labelthat makes one method of application legal with oneproduct and illegal with another, even though the activeingredient is identical.

Grazing restrictions mandate how long animals mustbe kept off treated pastures or how many days before

25

UH–CTAHR

slaughter the animal must be removed from treated pas-tures. Grazing restrictions are more severe for lactatingdairy animals than for meat animals. The restrictionsare aimed at preventing herbicide residues from con-taminating milk and meat. Herbicides applied accord-ing to label directions do not represent a threat to ani-mal health.

Included in this listing are herbicides for pasturesand natural areas. For aquatic sites refer to Vandiver(109).Pesticides labels and regulations are frequently changed,so it is the responsibility of the user to read and heed thelabel to ensure compliance.

Table A-1. The rating scale of toxins and example substances.Each pesticide product is assigned a signal word to warn users of its toxicity. The signal words (printed on the label) and theirapproximate hazards are listed in Table 3.

Toxcity Oral LD50

rating Category (mg/kg bodyweight) Example (with LD50)

1 Extremely Toxic < 5 Parathion (2)

2 Very Toxic 5–49 Vitamin D (10), dinoseb (40)

3 Moderately Toxic 50–499 Nicotine (50), paraquat (150), caffeine (200)

4 Slightly Toxic 500–4999 2,4-D (700), aspirin (750), bleach (2000), triclopyr (2140),

table salt (3320)

5 Almost Non-toxic 5000–14,999 Glyphosate (5000), picloram (8200)

6 Non-toxic 15,000+

Table A-2. Pesticide toxicity signal words and approximatelethal dose.

Signal word Amount needed to kill a 150-lb human

DANGER 1 teaspoon or less

WARNING 1 teaspoon to 1 tablespoon

CAUTION 1 ounce to 1 pint

26


Clo

pyr

alid

Tran

slin

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Ap

plic

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lan

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oil

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ula

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Use

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ectiv

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stem

erge

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con-

tro

l o

f a

nn

ua

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pe

ren

nia

lb

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dle

ave

s in

pa

stu

res

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as.

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ffec-

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on

mo

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um

es

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clud

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ffect

ive

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ies

in th

e U

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at 0

.5 lb

/acr

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), a

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d

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nsl

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ph

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nd

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on

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ype

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ause

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w a

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, m

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era

tele

ach

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. N

ot

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o

rph

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ded.

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rada

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by m

icro

bes.

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f-l i f

e 12

–70

days

in a

ran

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f soi

ls.

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tox

icity

to

fish

and

bird

s. L

D50

for

rats

>50

00 m

g/kg

.

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: L

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tre

ate

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ld b

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onun

trea

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ures

bef

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rea

s. L

ive

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pin

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ma

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ave

enou

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lid to

inju

re b

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ps.

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DA

lthou

gh th

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men

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re s

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r 2,

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, rel

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nd 2

,4-D

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ertie

s. M

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list

ed s

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atel

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hese

com

poun

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re o

ften

used

in c

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ally

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ulat

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ixtu

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Am

ine

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® (

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road

leaf

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PB

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don)

Sab

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tte)

Sav

age®

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eeda

r 64

® (

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Est

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Sal

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Con

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y b

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stu

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an

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atu

ral

are

as.

Est

ab

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ed

g

rass

es

very

tole

rant

exc

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for

som

e la

wn

spe

cie

s. S

en

siti

ve s

pe

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s:gu

ava,

joe

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ager

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.

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liar

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asa

lb

ark

(e

ste

rs o

nly

),an

d cu

t-su

rfac

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-st

ump)

.

A

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lia

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s tr

an

slo

-ca

ted

prim

arily

in th

e ph

loem

,ac

cum

ulat

ing

in t

he g

row

ing

poin

ts o

f ste

ms

and

root

s. It

sef

fect

is

horm

onal

; it

caus

esra

pid

but

abno

rmal

gro

wth

.T

he

ste

ms

an

d l

ea

ves

of

trea

ted

plan

ts c

urve

ext

rem

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and

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ticbe

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dea

th o

f the

pla

nt.

App

lied

at c

onve

ntio

nal r

ates

,2

,4-D

to

xici

ty

to

pla

nts

dis

sip

ate

s in

l–

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Alth

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.

Low

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ts is

300

–100

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. C

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ity:

2 ye

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feed

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tria

lso

n r

ats

an

d d

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spr

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fco

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and

num

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pur

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ed o

r use

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razi

ng:

for

lact

atin

g an

i-m

als

on p

astu

res

trea

ted

with

up

to 2

lb/a

cre,

7 d

ays

wit

hh

old

ing

. F

or

me

at

an

ima

ls,

no

with

ho

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als

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ures

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ated

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2 lb

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b

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Ap

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nB

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ior

in p

lan

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ior

in s

oil

Toxi

city

Reg

ula

tio

ns

Use

27

UH–CTAHR

Flu

azif

op

-p-b

uty

lF

usila

de D

X® o

r F

usila

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®

Ap

plic

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lan

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in s

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Use

Sel

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per

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ass

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o a

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on

dic

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. G

rass

grow

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ow r

ates

.

Pos

tem

erge

nce

folia

rap

plic

atio

n at

0.2

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cro

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l adj

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Rap

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abs

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in g

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ads

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ivity

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ave

rage

half-

life

in s

oils

15

days

so

low

risk

of g

roun

dwat

er c

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mi-

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LD50

in ra

ts 4

096

mg/

kg, l

ow to

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Unr

estr

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o no

t gra

ze tr

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eas.

Do

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thro

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irrig

a-tio

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Gly

ph

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ound

up O

rigin

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ound

up P

ro®, R

ound

up U

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; Rod

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r aq

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and

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onsa

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Sev

eral

new

pro

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s by

Mon

sant

o an

d ot

her

com

pani

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ow a

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ble.

Non

sele

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e bu

t esp

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lly e

ffec-

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agai

nst g

rass

es in

pas

ture

s,na

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as, a

quat

ic s

ites.

Con

-tr

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sedg

es,

herb

s, e

mer

ged

aqua

tics

by fo

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atio

n. S

e-ve

rely

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res

woo

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s by

fo-

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appl

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ion,

tho

ugh

not

usu-

ally

as

effe

ctiv

e as

hor

mon

e-ty

pehe

rbic

ides

, ex

cept

on

lant

ana.

Sev

eral

woo

dy s

peci

es v

ery

sen-

sitiv

e to

cut

-sur

face

tre

atm

ents

,in

clu

din

g

Ch

ine

se

ba

nya

n,

kara

kanu

t, pa

perb

ark,

rose

appl

e.

Fol

iar

spot

spr

ay a

ndcu

t-su

rfa

ce i

n p

as-

ture

s a

nd

fo

rest

s.B

roa

dca

st s

pra

y in

fore

sts

an

d i

n p

as-

ture

s fo

r p

ast

ure

reno

vatio

n.

Ab

sorb

ed

th

rou

gh

fo

liag

e.

Ra

infa

ll w

ithin

six

ho

urs

of

appl

icat

ion

may

was

h gl

ypho

-sa

te o

ff th

e fo

liage

and

redu

ceef

fect

iven

ess.

Tra

nslo

cate

dre

adily

in

phlo

em.

Mod

e of

actio

n: d

isru

pts

synt

hesi

s of

aro

ma

tic

am

ino

aci

ds

an

dth

us o

f pr

otei

ns.

Sym

ptom

ssl

ow to

app

ear.

So

stro

ngly

ads

orbe

d to

soi

lsas

to

rend

er it

inac

tive

imm

e-di

atel

y. P

oses

no

grou

nd w

a-te

r co

nta

min

ati

on

th

rea

t.R

eadi

ly d

ecom

pose

d by

soi

lm

icro

orga

nism

s. B

ecau

se o

fst

rong

ads

orpt

ivity

, ha

lf-lif

e in

soil

47 d

ays

but

non-

phyt

o-to

xic.

Lo

w t

oxi

city

. O

ral

LD

50 f

or

rats

49

00

mg/

kg.

Chr

onic

tox

-ic

ity s

tudi

es o

n ra

tsan

d do

gs f

ed u

p to

300

ppm

per

day

for

2 ye

ars

prod

uced

no

effe

cts.

Unr

estr

icte

d.G

razi

ng:

For

lact

atin

g an

i-m

als,

with

hold

14

days

af-

ter

spo

t a

pp

lica

tio

n,

56

days

afte

r bro

adca

st a

ppli-

catio

n. F

or m

eat

anim

als,

one

day

with

hold

ing

afte

rsp

ot a

pplic

atio

n, 5

6 da

ysaf

ter b

road

cast

app

licat

ion.

Ap

plic

atio

nB

ehav

ior

in p

lan

tsB

ehav

ior

in s

oil

Toxi

city

Reg

ula

tio

ns

UseDic

amb

aB

anve

l®, a

min

e sa

lt; C

larit

y®, D

GA

sal

t; V

eter

an® 1

0G (

BA

SF

)V

anqu

ish®

, DG

A s

alt (

Syn

gent

a)M

ixtu

res

Ap

plic

atio

nB

ehav

ior

in p

lan

tsB

ehav

ior

in s

oil

Toxi

city

Reg

ula

tio

ns

Use

Pos

tem

erge

nce

cont

rol o

f bro

a-d

lea

f w

ee

ds

incl

ud

ing

so

me

woo

dy p

lant

s in

pas

ture

s an

dna

tura

l ar

eas.

Pol

ygon

aceo

usw

eeds

(kam

ole,

spi

ny e

mex

) are

very

sen

sitiv

e. B

ur b

ush,

chr

ist-

mas

berr

y, f

alse

ele

phan

tsfo

ot,

guav

a ar

e se

nsiti

ve.

Fol

iar

spra

y, 0

.25–

8lb

/acr

e in

SV

R o

f 2–

40 g

al/a

cre.

Cut

-sur

face

Ab

sorb

ed

by

fol i

ag

e a

nd

root

s. T

rans

loca

tes

read

ily in

xyle

m a

nd p

hloe

m. H

orm

one

type

her

bici

de,

caus

es c

urv-

ing,

ben

ding

of s

tem

s, c

urlin

go

f le

ave

s. A

ccu

mu

late

s in

grow

ing

poin

ts i

n st

ems

and

root

s.

Low

to

med

ium

lea

chin

g po

-te

ntia

l in

soi

ls b

ut h

alf

life

isle

ss th

an l4

day

s in

war

m m

oist

soils

.

Low

tox

icity

to

fish,

bird

s an

d m

amm

als.

LD50

rat

s: 2

629

mg/

kg.

Unr

estr

icte

d.G

razi

ng:

For

lac

tatin

g an

i-m

als

on p

astu

res

trea

ted

with

≤1 ⁄2

lb/a

cre,

7 d

ays

with

-ho

ldin

g; 1

lb/a

cre,

21

days

;2

lb/a

cre,

40

days

; and

8 lb

/ac

re, 6

0 da

ys. F

or m

eat a

ni-

mal

s, n

o w

ithho

ldin

g bu

t re-

mo

ve a

nim

als

fro

m p

as-

ture

s tr

eate

d w

ith ≥

2 lb

/acr

e30

day

s be

fore

sla

ught

er.

28


Hex

azin

on

eV

elpa

r 90

W®, 9

0% w

etta

ble

pow

der

(DuP

ont)

Vel

par

L®, 2

5% m

isci

ble

liqui

d (D

uPon

t)P

rono

ne P

ower

Pel

lets

®, l

arge

pel

lets

for

grid

app

licat

ions

(D

uPon

t)

Ap

plic

atio

nB

ehav

ior

in p

lan

tsB

ehav

ior

in s

oil

Toxi

city

Reg

ula

tio

ns

Use

Non

sele

ctiv

e co

ntro

l of w

eeds

inpa

stur

es a

nd n

oncr

opla

nd.

Se-

lect

ivity

is a

chie

ved

by d

irect

edsp

ray

appl

icat

ions

and

by

“hot

spot

” app

licat

ions

to th

e so

il ne

arth

e ta

rget

wee

d w

here

the

root

sca

n ab

sorb

the

herb

icid

e.

App

ly V

elpa

r L in

spo

ts to

the

soil

with

an

exac

tde

liver

y gu

n ap

plic

ator

with

in 3

ft

of s

tem

at

2–4

ml p

er in

ch s

tem

dia

met

er, n

ot to

exc

eed

0.33

gal

per

acr

e pe

r ye

ar (

300

1-in

ch s

tem

equi

vale

nts

per

acre

). W

here

mul

tiple

app

li-ca

tions

are

req

uire

d, a

pply

at o

ppos

ite s

ides

of p

lant

. Do

not a

pply

to s

tand

ing

wat

er, i

rri-

gatio

n di

tche

s or

mar

shes

as

hexa

zino

ne is

very

sol

uble

. Do

not a

pply

to th

ick

clay

soi

ls.

Do

not

appl

y ne

ar d

esira

ble

plan

ts (

with

in a

dist

ance

equ

al to

3 ti

mes

the

heig

ht o

r can

opy

diam

eter

, whi

chev

er is

gre

ater

). B

oth

Vel

par

L an

d V

elpa

r 90

W m

ay b

e ap

plie

d to

the

foli-

age

of ta

rget

pla

nts

in s

pot a

pplic

atio

n. H

ow-

ever

, th

e sp

raye

d ar

ea w

ill r

emai

n ba

re f

orse

vera

l mon

ths.

Pro

none

Pow

er P

elle

ts m

aybe

app

lied

in 3

-ft

grid

app

licat

ions

to

targ

eton

e or

mor

e pl

ants

.

Abs

orbe

d by

root

s an

dfo

l iag

e.

Tra

nsl

oca

tes

via

the

xyle

m.

Inhi

bits

phot

osyn

thes

is.

Mob

ile a

nd s

uffic

ient

lyp

ers

iste

nt

(ha

lf-l i f

e 9

0da

ys)

to h

ave

pote

ntia

lfo

r g

rou

nd

wa

ter

con

-ta

min

atio

n in

hig

h ra

in-

fall

area

s.

Lo

w t

oxi

city

to

fish,

wi ld

l ife

and

ma

mm

als

. L

D5

0

rats

l690

mg/

kg.

Unr

estr

icte

d.G

razi

ng: w

ithho

ldfo

r 30

day

s af

ter

appl

icat

ion.

Ap

plic

atio

nB

ehav

ior

in p

lan

tsB

ehav

ior

in s

oil

Toxi

city

Reg

ula

tio

ns

UseIm

azap

yrA

rsen

al® (

BA

SF

)C

hopp

er® (

BA

SF

)C

hopp

er R

TU

®, r

eady

-to-

use

(BA

SF

)

Non

sele

ctiv

e pr

eem

er-

ge

nce

an

d p

ost

em

er-

genc

e co

ntro

l of

gra

ssan

d br

oadl

eaf

wee

ds i

nfo

rest

s an

d w

ildlif

e op

en-

ings

.

Fol

iar 1

lb a

ctiv

e/ac

re, b

asal

bar

k,st

umps

.

Str

ongl

y ad

sorb

ed in

aci

dso

ils a

nd h

igh

clay

and

or-

gani

c m

atte

r so

ils.

Doe

sno

t le

ach.

No

runo

ff in

tofo

rest

str

ea

ms.

Ra

pid

lyd

eg

rad

es

in

sha

llo

wpo

nds.

Rea

dily

abs

orbe

d vi

a fo

li-a

ge

an

d r

oo

ts.

Tra

nsl

o-

cate

s vi

a x

yle

m a

nd

ph

-lo

em.

Inte

rfer

es w

ith s

yn-

thes

is o

f pro

tein

s.

Low

toxi

city

to fi

sh,

wild

life

and

mam

-m

als

. L

D5

0 r

ats

,50

00+

mg/

kg.

Unr

estr

icte

d.W

eeds

can

dev

elop

cro

ss r

e-si

stan

ce b

etw

een

sulfo

nylu

reas

(e.g

., m

ets

ulfu

ron

, su

lfom

et-

uron

) and

imid

azol

inon

es (e

.g.,

imaz

apyr

) if

any

one

or c

ombi

-na

tion

of th

ese

type

s of

che

mi-

cals

are

use

d re

peat

edly

ove

r4–

6 ye

ars.

The

se h

erbi

cide

ssh

ould

be

alte

rnat

ed w

ith h

er-

bici

des

with

diff

eren

t mod

es o

fac

tion.

Pre

cau

tio

ns

29

UH–CTAHR

MC

PA

MC

P A

min

e 4®

(C

lean

Cro

p)

Sel

ectiv

e co

ntro

l of

bro

adle

afw

eeds

(e.

g.,

joee

, M

adag

asca

rra

gwor

t, tr

opic

age

ratu

m,)

and

som

e se

nsiti

ve w

oody

wee

dssu

ch a

s gu

ava

in p

astu

res,

for

-es

ts a

nd n

on-c

rop

area

s.

Fol

iar,

1-2

lb/a

cre

and

cut

surf

ace

in

pa

s-tu

res.

Non

-cro

p la

ndup

to 3

lb/a

cre.

Leg

umes

sen

sitiv

e.

Ap

plic

atio

nB

ehav

ior

in p

lan

tsB

ehav

ior

in s

oil

Toxi

city

Reg

ula

tio

ns

Use

Rea

dlily

abs

orbe

d by

leav

es.

Phl

oem

mob

ile.

Not

per

sist

ent.

Mob

ility

not

apr

oble

m g

iven

sho

rt h

alf-

life

of6

days

in w

arm

, moi

st s

oils

.

Slig

htly

to

xic.

Ora

lLD

50 in

mic

e 65

0 m

g/kg

bod

ywei

ght.

Unr

estr

icte

d.R

emov

e m

eat

anim

als

tobe

sla

ught

ered

from

trea

ted

lan

d

on

e

we

ek

be

fore

slau

ghte

r or a

fter M

CP

A a

p-pl

icat

ion.

Do

not g

raze

milk

an

ima

ls o

n t

rea

ted

la

nd

with

in 1

wee

k of

trea

tmen

t.

Met

sulf

uro

nE

scor

t®, 6

0% d

ry fl

owab

le (

DuP

ont)

Ally

®, 6

0% d

ry fl

owab

le (

DuP

ont)

Sel

ectiv

e co

ntro

l of

di-

cots

in

pa

stu

res

an

dno

ncro

plan

d. K

ahili

gin

-ge

r, y

ello

w g

inge

r an

dw

hite

gin

ger v

ery

sens

i-tiv

e (0

.5 o

z. p

rodu

ct /

acre

).

Fol

iar

spra

y 0.

06-0

.45

oz a

ctiv

e/ac

re,

with

an

effe

ctiv

e su

rfac

tant

, in

20-1

00 g

al/a

cre.

Ver

y lo

wdo

ses

effe

ctiv

e. E

xtre

me

prec

autio

ns s

houl

d be

take

n to

pre

vent

drif

t and

in c

lean

ing

equi

pmen

t.W

eeds

can

dev

elop

cro

ss r

esis

tanc

e be

twee

nsu

lfony

lure

as (

e.g.

, m

etsu

lfuro

n, s

ulfo

met

uron

)an

d im

idaz

olin

ones

(e.

g.,

imaz

apyr

) if

any

one

or c

ombi

natio

n of

thes

e ty

pes

of c

hem

ical

s ar

eus

ed r

epea

tedl

y ov

er 4

-6 y

ears

.

Rea

dily

abs

orbe

d by

foli-

age

and

root

s. T

rans

lo-

cate

s re

adily

in th

e xy

lem

and

less

so

in th

e ph

loem

.

Ads

orpt

ion

to c

lays

is lo

w;

leac

habl

e, b

ut b

iode

gra-

datio

n is

rapi

d. H

alf-

life

isl-6

wee

ks.

Low

toxi

city

tofis

h, w

ildlif

e an

dm

amm

als.

LD

50

rats

>50

00 m

g/kg

.

Unr

estr

icte

d.N

o gr

azin

g re

stric

-tio

ns.

Ap

plic

atio

nB

ehav

ior

in p

lan

tsB

ehav

ior

in s

oil

Toxi

city

Reg

ula

tio

ns

Use Par

aqu

atO

rtho

Par

aqua

t® C

L (C

hevr

on)

Gra

mox

one®

(Z

enec

a)

Non

-sel

ectiv

e. A

pply

as

folia

rsp

ray

for

supp

ress

ion

of e

xist

-in

g ve

geta

tion

e.g.

, fo

r pa

stur

ere

no

vati

on

. M

atu

re

pla

nts

read

ily r

ecov

er fr

om tr

eatm

ent.

Fol

iar

spra

y.V

ery

rapi

dly

abso

rbed

by

foli-

age.

Ver

y re

sist

ant

to w

ash-

ing

by r

ain.

Mod

e of

act

ion:

Con

tact

. D

estr

uctio

n of

cel

lm

embr

anes

in

the

pres

ence

of s

unlig

ht. N

o br

eakd

own

ofpa

raqu

at in

pla

nts.

Str

on

gly

an

d i

mm

ed

iate

lyad

sorb

ed t

o cl

ay m

iner

als

inso

ils.

Soi

l-bou

nd p

araq

uat

ispe

rsis

tent

but

bio

logi

cally

inac

-tiv

e. It

will

be

slow

ly d

egra

ded.

Mo

de

rate

ly t

oxi

c,a

cute

ora

l L

D5

0 i

nra

ts i

s 1

20

mg

/kg

.C

hron

ic t

oxic

ity t

ri-

als,

2 y

ears

at u

p to

l70

pp

m p

ara

qu

at

per d

ay p

rodu

ced

noef

fect

in r

ats.

Res

tric

ted

use,

irre

vers

ibly

toxi

c if

swal

low

ed.

Spe

cial

perm

it fr

om th

e H

awai

i De-

part

men

t of

Agr

icul

ture

re-

quire

d.

Ap

plic

atio

nB

ehav

ior

in p

lan

tsB

ehav

ior

in s

oil

Toxi

city

Reg

ula

tio

ns

Use

30


Pic

lora

mTo

rdon

22K

®, p

otas

sium

sal

t (D

ow A

groS

cien

ces)

Woo

dy p

lant

con

trol

, fo

liar

and

cut-

surf

ace

appl

icat

ions

in p

as-

ture

s. G

rass

es to

lera

nt, c

ruci

fer-

ous

plan

ts (

cabb

age

fam

ily)

tol-

eran

t. W

ide

spec

trum

of

dico

tsp

eci

es

susc

ep

tible

in

clu

din

gbl

ack

wat

tle,

cact

us,

cats

claw

,ch

ristm

asbe

rry,

gor

se,

lant

ana,

faya

tree

, hila

hila

, jav

a pl

um, k

oaha

ole,

ros

eapp

le.

Fol

iar

spra

y, c

ut-

surf

ace

appl

icat

ion.

Rea

dily

abs

orbe

d by

fol

iage

and

by r

oots

. R

eady

tra

nslo

-ca

tion

in x

ylem

and

phl

oem

.M

ode

of a

ctio

n: h

orm

onal

.

Can

be

pers

iste

nt, h

alf-

life

20-

300

days

, and

mob

ile in

san

dy,

low

org

anic

mat

ter

soils

. B

e-ca

use

of p

ersi

sten

ce, e

xtre

me

caut

ion

shou

ld b

e ex

erci

sed

toav

oid

drift

and

oth

er f

orm

s of

cont

amin

atio

n of

cro

plan

d an

dsi

mi la

rly s

ensi

tive

non-

targ

etar

eas.

Thi

s in

clud

es k

eepi

ngl i

vest

ock

gra

zin

g r

ece

ntl

ytr

ea

ted

pa

stu

res

fro

m c

rop

-la

nd

. P

iclo

ram

w

ill

pa

ssth

roug

h an

imal

s ra

pidl

y an

dun

alte

red.

Pic

lora

m is

sen

sitiv

eto

pho

tode

com

posi

tion.

Low

ord

er o

f tox

icity

.O

ral

LD50

for

rat

s is

8200

mg/

kg. C

hron

icto

xici

ty

tria

ls

(2ye

ars

, l5

0 m

g/k

g/

da

y) o

n r

ats

an

dd

og

s p

rod

uce

d n

oef

fect

s.

Res

tric

ted

use.

Spe

cial

per

-m

it fr

om

Ha

wa

ii D

ep

art

-m

en

t o

f A

gri

cult

ure

re

-qu

ired.

Spo

t spr

ayin

g on

ly.

Ha

zard

to

n

on

-ta

rge

tpl

ants

, gr

ound

wat

er c

on-

tam

inat

ion

pote

ntia

l.G

razi

ng:

For

lact

atin

g an

i-m

als

14 d

ays

with

hold

ing.

For

mea

t an

imal

s on

pas

-tu

res

trea

ted

with

up

to 1

lb/

acre

no

with

hold

ing,

but

re-

mov

e 3

days

bef

ore

slau

gh-

ter

durin

g th

e 2

wee

ks f

ol-

low

ing

trea

tmen

t.

Ap

plic

atio

nB

ehav

ior

in p

lan

tsB

ehav

ior

in s

oil

Toxi

city

Reg

ula

tio

ns

Use Su

lfo

met

uro

nO

ust®

, dis

pers

able

gra

nule

s (D

uPon

t)

Non

sele

ctiv

e pr

eem

erge

nce

and

post

emer

genc

e co

ntro

lof

wee

ds in

nat

ural

are

as.

Fo

liar

2.2

5–

8 o

zac

tive/

acre

.A

bsor

bed

via

root

s an

dfo

liage

. Tr

ansl

ocat

es i

nbo

th x

ylem

and

phl

oem

.In

hibi

ts p

rote

in s

ynth

e-si

s.

Mob

ility

in a

cid

soils

and

high

org

anic

mat

ter

soils

po

ore

r th

an

in

alk

alin

eso

ils a

nd

lo

w o

rga

nic

mat

ter

soils

. Soi

l hal

f-lif

ein

aci

d so

ils 2

0–28

day

s.

Low

tox

icity

to

fish,

bird

s an

d m

amm

als.

Ora

l L

D5

0 i

n r

ats

gre

ate

r th

an

50

00

mg/

kg.

Bec

ause

sul

fom

etur

on i

s ef

fect

ive

at l

owra

tes,

avo

id d

rift a

nd a

pplic

atio

n to

bar

e so

ilw

here

win

d ca

n bl

ow tr

eate

d so

il on

to s

en-

sitiv

e pl

ants

. W

eeds

can

dev

elop

cro

ss r

e-si

stan

ce b

etw

een

sulfo

nylu

reas

(e.

g.,

met

-su

lfuro

n, s

ulfo

met

uron

) and

imid

azol

inon

es(e

.g.,

imaz

apyr

) if

any

one

or c

ombi

natio

nof

thes

e ty

pes

of c

hem

ical

s ar

e us

ed re

peat

-e

dly

ove

r 4

–6

ye

ars

. T

he

se h

erb

icid

es

shou

ld b

e al

tern

ated

with

her

bici

des

with

dif-

fere

nt m

odes

of a

ctio

n.

Ap

plic

atio

nB

ehav

ior

in p

lan

tsB

ehav

ior

in s

oil

Toxi

city

Pre

cau

tio

ns

Use

31

UH–CTAHR

Tric

lop

yrG

arlo

n 3A

®, a

min

e sa

lt (D

ow A

groS

cien

ces)

Gar

lon

4®, e

ster

(D

ow A

groS

cien

ces)

Pat

hfin

der

II, e

ster

, rea

dy-t

o-us

e (D

ow A

groS

cien

ces)

Red

eem

®, a

min

e sa

lt (D

ow A

groS

cien

ces)

Rem

edy

, est

er (

Dow

Agr

oSci

ence

s)

Con

trol

s br

oadl

eave

s in

clud

ing

woo

dyp

lan

ts i

n p

ast

ure

s a

nd

na

tura

l a

rea

s.C

hri

stm

asb

err

y, d

ow

ny

rose

myr

tle

,F

orm

osan

koa

, gor

se, g

uava

, str

awbe

rry

guav

a, h

ighb

ush

blac

kber

ry,

Java

plu

m,

me

last

om

a,

nig

ht-

blo

om

ing

ce

reu

s,th

imbl

eber

ry,

velv

et t

ree,

yel

low

Him

a-la

yan

ra

spb

err

y se

nsi

tive

. D

ow

ny

rose

myr

tle, l

anta

na, M

adag

asca

r rag

wor

tto

lera

nt o

f fol

iar a

pplic

atio

ns. M

any

woo

dysp

ecie

s se

nsiti

ve t

o cu

t-su

rfac

e or

bas

alba

rk a

pplic

atio

ns in

clud

ing

lant

ana,

kia

we,

dow

ny r

osem

yrtle

.

Fol

iar

spra

y,b

asa

l b

ark

(est

er)

an

dcu

t-su

rfac

e.

Rea

dily

abs

orbe

d by

folia

ge

an

d r

oo

ts.

Tran

sloc

ates

in

the

ph

loe

m.

Mo

de

of

actio

n: h

orm

onal

.

Mob

ile in

soi

ls. D

e-gr

aded

by

mic

roor

-ga

nism

s an

d su

n-lig

ht.

Ave

rage

hal

flif

e: 1

0–46

day

s.

Low

ord

er o

f to

x-ic

ity.

Acu

te o

ral

LD

50 f

or

rats

is

2l40

mg/

kg.

Unr

estr

icte

d.G

razi

ng

: F

or

lact

atin

g a

nim

als

on

pa

stu

res

trea

ted

with

up

to 2

lb/

acre

, 14

day

s w

ithho

ld-

ing,

for

rat

es b

etw

een

2–6

lb/a

cre,

no

graz

ing

until

the

next

gro

win

g se

ason

. For

oth

er li

vest

ock

on p

astu

res

trea

ted

with

up

to 2

lb/a

cre,

no

with

-ho

ldin

g bu

t rem

ove

thre

e da

ys b

efor

e sl

augh

ter

durin

g ye

ar o

f ap

plic

atio

n. O

n pa

stur

es t

reat

edw

ith r

ates

bet

wee

n 2–

6 lb

/acr

e, 1

4 da

ys w

ith-

hold

ing

and

rem

ove

thre

e da

ys b

efor

e sl

augh

ter

durin

g ye

ar o

f ap

plic

atio

n. I

f le

ss t

han

25%

of

the

past

ure

is tr

eate

d, n

o gr

azin

g re

stric

tion.

Ap

plic

atio

nB

ehav

ior

in p

lan

tsB

ehav

ior

in s

oil

Toxi

city

Reg

ula

tio

ns

UseTeb

uth

iuro

nS

pike

20

P®, p

elle

ts (

Dow

Agr

oSci

ence

s)

Fo

r co

ntr

ol

of

dic

ots

in

clu

din

gw

oody

pla

nts

by s

oil a

pplic

atio

nsin

pas

ture

s an

d w

ildlif

e op

enin

gs.

Eff

ect

ive

on

ch

rist

ma

sbe

rry,

gu

ava

, st

raw

be

rry

gu

ava

, ko

ah

ao

le,

Ma

da

ga

sca

r ra

gw

ort

,sh

oe

bu

tto

n a

rde

sia

. P

oo

r o

nd

ow

ny

rose

myr

tle

, fa

yatr

ee

,F

orm

osan

koa

, gor

se.

App

licat

ion

ofg

ran

ule

s to

grou

nd, 0

.75–

3.0

lb a

ctiv

e/ac

re.

Abs

orbe

d th

roug

h th

ero

ots,

poo

rly th

roug

h fo

-l ia

ge.

Rea

dily

tra

nslo

-ca

ted

in x

ylem

. Mod

e of

actio

n: p

hoto

synt

hesi

sin

hibi

tor.

Ver

y pe

rsis

tent

in s

oils

,ha

lf-lif

e of

l2–l

5 m

onth

s.M

ore

pers

iste

nt i

n dr

yso

i ls a

nd h

igh

orga

nic

mat

ter s

oils

. Poo

r mob

il-ity

in s

oils

.

Slig

htly

toxi

c. O

ral

LD

50 f

or

rats

is

644

mg/

kg. T

hree

gene

ratio

ns fe

ed-

ing

tria

ls in

dica

teno

toxi

city

to ra

ts.

Unr

estr

icte

d.G

razi

ng: U

p to

20

lb p

rod

uct

/acr

e,

no w

ithho

ldin

g.

Ap

plic

atio

nB

ehav

ior

in p

lan

tsB

ehav

ior

in s

oil

Toxi

city

Reg

ula

tio

ns

Use

Hig

her

dose

s, 1

5 lb

prod

uct/a

cre

or h

ighe

r ,ca

n in

jure

gra

sses

.

Pre

cau

tio

ns

32


Appendix 2.Common and Botanical Namesof Weeds Mentioned in the Text

Listed here are the botanical names of weeds of Hawaiimentioned in this publication. For additional informa-tion on these weeds, see Wagner et al.(110), Neal(81), andHaselwood et al.(41). Color photographs of some of theseweeds may be found in Pratt(91) or Whistler(115). Color

photos and management notes may be found in Lorenziand Jeffery(63), Motooka et al.(78), and in the forthcomingCTAHR publication, Weeds of pastures and natural ar-eas of Hawaii and their management, by Motooka etal., in preparation.

Common name Botanical name

ageratum, tropic Ageratum conyzoidesapple-of-Sodom Solanum linnaeanumardesia, shoebutton Ardesia ellipticabanyan, Chinese Ficus microcarpablackberry, highbush Rubus argutusblack wattle Acacia mearnsiibur bush Triumfetta rhomboideacactus, prickly pear Opuntia ficus-indicaCaliforniagrass Brachiaria muticacatsclaw Caesalpinia decapetalachristmasberry Schinus terebinthifoliusdowny rosemyrtle Rhodomyrtus tomentosaelephantsfoot, false Elephantopus spicatusemex, spiny Emex spinosafaya tree Myrica fayaFormosan koa Acacia confusafountaingrass Pennisetum setaceumginger, kahili Hedychium gardnerianumginger, white Hedychium coronariumginger, yellow Hedychium flavescensgorse Ulex europaeusguava Psidium guajavaguava, strawberry Psidium cattleianumguineagrass Panicum maximumhamakua pamakani Ageratina ripariahilahila Mimosa pudicahuehue haole Passiflora suberosa

Common name Botanical name

java plum Syzygium cuminiJob’s tears Coix lacharyma-jobijoee Stachytarpheta dichotomakamole Polygonum glabrumkarakanut Corynocarpus laevigatuskiawe Prosopis pallidakoa haole Leucaena leucocephalalantana Lantana camaraMadagascar ragwort (fireweed) Senecio madagascariensisMaui pamakani Ageratina adenophoraMauritius hemp Furcraea foetidamelastoma Melastoma candidummolucca albizia Paraserianthes falcatariamorningglory, Indian Ipomea indicanightblooming cereus Hylocereus undatuspalmgrass Setaria palmifoliapaperbark Melaleuca quinquenervapluchea, Indian Pluchea indicaragweed parthenium Parthenium hysterophorusraspberry, yellow Himalayan Rubus ellipticusroseapple Syzygium jambosSacramento bur Triumfetta semitrilobasourbush Pluchea carolinensisthimbleberry Rubus rosaefoliusturkeyberry Solanum torvumvelvet tree Miconia calvescens

33

UH–CTAHR

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2. Ames, B.N. 1983. Dietary carcinogens and anticarcinogens. Sci-ence 221(4017):1256–1264.

3. Ames, B.N. 1993. Science and the environment: facts vs. phan-toms. Priorities winter:42–43.

4. Ames, B.N., R. Magaw, and L.S. Gold. 1987. Ranking possiblecarcinogenic hazards. Science 236:271–280.

5. Amor, R.L. 1975. Ecology and control of blackberry (Rubusfruticosis L. agy.) IV. Effect of single and repeated applicationsof 2,4,5-T, picloram, and aminotriazole. Weed Res. 15:39–45.

6. Amor, R.L. 1975. Ecology and control of blackberry (Rubusfruticosus L. agy.); V. Control by picloram granules. Weed Res.15:47–52.

7. Amor, R.L., and R.G. Richardson.1980. The biology of Austra-lian weeds. 2. Rubus fruticosis L. Agy. J. Australian Inst. Agri.Sci. 46:87–97.

8. Anderson, W.P. 1983. Weed science: principles. 2nd ed. WestPubl. New York. 655p.

9. Anonymous. 1987. Researchers cite need for more water qualitystudies. Conserv. Till. News. pp. 1–2.

10. Asher, J.E. 2001. Wildlife habitat: a compelling case for weedmanagement. Abstr., Weed Sci. Soc. Amer. 41:94–95. Greens-boro, N.C.

11. Ashton, F.M., and A.S Crafts. 1973. Mode of action of herbi-cides. Wiley, New York.

12. Badiei, A.A., E. Basler, and P.W. Santlemann. 1966. Aspects ofmovement of 2,4,5-T in blackjack oak. Weeds 14:302–305.

13. Balneaves, J.M. 1980. A programme for gorse control in for-estry using a double kill spray regime. Proc. 33rd New ZealandWeed and Pest Control Conf. pp. 170–173.

14. Balneaves, J.M. 1985. Effect of herbicides on gorse in a dryyear. Proc. 38th New Zealand Weed and Pest Control Conf. 38:92–93,

15. Balneaves, J.M. 1985. The effect of added surfactant on theperformance of scrubweed herbicides. Proc. 38th New ZealandWeed and Pest Control Conf. 38:98–101.

16. Balneaves, J.M., and B.J. Frederic. 1988. Silwet M improvesperformance of glyphosate on gorse. Proc. 41st New ZealandWeed and Pest Control Conf. pp. 146–148. Aukland.

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20. Behrens, R., and M.A. Elakkad. 1981. Influence of rainfall onphytotoxicity of foliarly applied 2,4-D. Weed Sci. 29:349–355.

21. Bocquet, Aime. 1979. Lake bottom archeology. Sci. Amer.

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34


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51. Hay, J.R., and K.V. Thimann. 1956. The fate of 2,4-dichlo-rophenoxyacetic acid and its breakdown in the plant. PlantPhysiol. 31:382–387.

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54. Ivens, G.W. 1979. Effects of sprays on gorse regrowth at dif-ferent growth stages. Proc. 32nd New Zealand Weed and PestControl Conf., Dunedin, New Zealand. pp. 303–306.

55. Jansen, L.L. 1964. Surfactant enhancement of herbicide entry.Weeds 12:251–255.

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58. Klingman, G.C., and F.M. Ashton. 1975. Weed science prin-ciples and practices. Wiley, New York. 431 pp.

59. Lane, P.M.S., and O.L. Park. 1984. Gorse control withglyphosate. Proc. New Zealand Weed and Pest Control Conf.37:194–196.

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62. Leonard, O.A., and A.S. Crafts. 1956. Translocation of herbi-cides III. Uptake and distribution of radioactive 2,4-D by brushspecies. Hilgardia 26:366–415.

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