management of himalayan blackberry in sw oregon

Managing Himalayan Blackberry in SW Oregon

Extension Service Southern Oregon Research & Extension Center Oregon State University, 569 Hanley Road, Central Point, Oregon 97502-1251 T 541-776-7371| F 541-776-7373 | http://extension.oregonstate.edu/sorec/

MANAGING HIMALAYAN BLACKBERRY IN SW OREGON

Southern Oregon Forestry Note #7 Max Bennett, OSU Extension Service

Introduction

Himalayan blackberry (HB, Rubus discolor, Rubus procerus) is one of our most challenging noxious weeds problems. An invader of riparian zones, roadsides, woodlands, open forests and disturbed areas, HB is difficult to eradicate once established and tends to outcompete native vegetation. This article briefly reviews the biology of HB, its ecological impacts, and strategies for managing HB infestations. HB Growth Habits and Reproduction HB is a native of Western Europe that was introduced in the United States as a crop in the late 19th century. "Burbank's Frankenstein" (after horticulturist Luther Burbank) is thought to have become naturalized in the West Coast around 1945. Commonly found in riparian areas, it also occurs along roadsides,

Figure 1. Typical blackberry thicket along Jackson Creek near Central Point, Oregon

Figure 2. Typical HBB-dominated understory in a riparian area. Little or no recruitment of native trees and shrubs is evident.

fence corridors, and other disturbed sites. HB occurs mainly in areas with precipitation of at least 29 inches

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(Hoshovsky 1989); it is also found on moist but well drained sites in more arid areas such as interior southwestern Oregon. HB is a robust, semi-evergreen shrub that can grow to nearly 10 ft in height (Tirmenstein 1989), with individual canes extending as much as 23 ft in a single season. Canes or stems are biennial. First year canes develop from buds at or below the ground surface and bear only leaves. Second year canes arise the axils of the first year canes (primocanes) and bear both leaves and flowers. A distinctive feature of HB is the stout cane which, when dead, provides a supporting architecture for live canes that sprawl over it, ultimately forming a nearly impenetrable thicket. Stem density has been reported at 525 canes per square meter (Hoshovsky

1989). In several SW Oregon field trials, maximum plant density was about 25 per square meter (with each plant representing one burl or root crown from which multiple canes typically emerge).

HB can produce vast numbers of seeds, up to 13,000 per square meter (Hoshovsky 1989). The seeds, contained in berries highly palatable to both humans and wildlife, are typically spread by birds and small mammals. Seeds are thought to remain viable in the soil for several years (Tirmenstein 1989). Thus a significant concern in restoration efforts in the potential germination of new blackberry plants from the soil seed bank even when existing plants have largely been eradicated. However, seedlings grow much more slowly than daughter plants, i.e., those resulting from vegetative reproduction. The vigorous reproduction of HB by vegetative means is one of its most notable features. Anyone grubbing blackberry roots will encounter one of the large root crowns or “burls” from which many stout lateral and smaller fibrous roots emerge (Figure 3). Roots

Figure 3. HB root crown or "burl"

Figure 4. New canes emerging from rhizomes (underground creeping stems).

have been found at depths of 35 inches and up to 34 ft in length. Shoots (new canes) emerge from the root crowns and

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roots at depth up to 18 inches (Hoshovsky 1989) (Figure 4). HB will propagate from root fragments and stem cuttings, making it a challenge to remove all potential rooting material when digging or grubbing. Fallen canes will root at the tips (Figure 5) and nodes, contributing to the rapid spread of plants. According to one study, in less than two years a cane cutting can produce a thicket 16-ft in diameter (Amor 1973). In several SW Oregon field trials the average height of canes one year after a cutting to ground level was 41”, with individual canes has tall as 60”. Of significance for manual and mechanical HB control efforts, repeated mowings or slashings appear to increase the formation of suckers from lateral roots and induce branching (DiTomaso 2000).

Ecological Impacts of HB The threat posed by exotic species – including HB – to the health of lowland riparian zones is widely recognized (Gregory 1999, Massingill 2003), but published data on the extent and impact

of HB in riparian zones is scant. Casual observation suggests that HB is sometimes found as scattered plants or clumps of plants within a matrix of native vegetation. Frequently, small clumps or islands of trees occur within larger patches of HB that form a virtual monoculture. Even where tree cover is significant, HB often dominates the understory. Why is HB so dominant? Several reasons can be suggested:

• HB rapidly occupies areas disturbed by flooding and scarification, both through vegetative means and by seed.

• HB outcompetes most native vegetation for site resources, primarily soil moisture and sunlight

• Once established, HB appears to be persistent and self-maintaining, in the absence of disturbance

• Under natural conditions, most native trees and shrubs require partial to full sunlight and a temporary reprieve from other competing vegetation to become established, but these conditions are absent in HB-dominated riparian zones.

• We have removed or reduced the primary riparian disturbance – flooding – which sets the stage for regeneration of many native trees and shrubs. For example, black cottonwood (Populus trichocarpa) and alder (Alnus spp) both require full sunlight, mineral soil, and temporary freedom from vegetative competition to become established, conditions that historically were provided by

Figure 5. Daughter plant from tip rooting.

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frequent floods. Currently, active recruitment of these species in occurring primarily near stream channels scoured by annual high flows.

As a result, succession in many HB-dominated riparian zones, in the absence of flooding, is trending towards a stable community dominated by HB with relatively few trees. A similar trend has been observed in some western river systems where invasion by exotic species combined with a reduction in disturbance (flooding) is reducing recruitment of native cottonwood trees (Howe and Knopf 1991, Lesica and Miles 1999). The trend toward dominance by a stable shrub community parallels conditions described by Hibbs et al (2001) for forests in the Oregon coast range. From the standpoint of riparian function, HB may help filter sediments, capture excessive nutrients, and maintain streambank stability. HB has even been planted for erosion control purposes (Tirmenstein 1989). However, for many key riparian functions, HB is inferior to native riparian vegetation. Obvious differences relate to shade production and inputs of large wood. HB thickets provide some habitat values but overall plant and animal diversity is likely to be significantly lower in these areas. In addition, anecdotal evidence suggests that compared to native trees, HB root strength and density is much less than that of native trees such as alder and cottonwood. HB Management Case Studies Recent SW Oregon Field Trials

Since 2000, several small scale field trials have been installed in interior southwestern Oregon (Jackson County) to evaluate methods for controlling HB. The trials investigated combinations of mowing, hand slashing, grubbing, goat browsing, and herbicide application for both site preparation and release of planted trees and shrubs on HB-dominated sites. The general effects of these treatments are known but we wanted to quantify their specific effects on southwestern Oregon sites in the context of projects designed to establish native trees and shrubs in streamside areas and adjacent terraces. The trials also explored the suitability of several different tree and shrub species for southwestern Oregon riparian sites, the use of various stock types, and the influence of summer irrigation on tree survival and growth, but only the results relating to HB management are reported here. Although interior southwestern Oregon is significantly more arid than other parts of western Oregon, HB is still a significant component of lowland riparian zones. Trial #1 -Methods tested: Mowing + herbicides, goat browsing Mowing + herbicide treatment: HB-dominated patches were mowed with a brush hog to stubble height in May and again in July. Sprouting canes were spot-sprayed with Roundup (glyphosate) in late September, and were again mowed to stubble height in late fall. These areas were planted in November. The area within a 3’ (0.9 m) radius around each tree was spot sprayed with Roundup the following April to release the trees from herbaceous competition. The area within 2’ (0.6 m) of each tree was hand-weeded in July.

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Results: In mid-April of the year following tree planting, average blackberry cover was less than 5%; by mid-August the average cover was about 7%, with much of this represented by plants regenerating from seed, not sprouts. The most abundant vegetation on the treated plots in addition to the planted trees was hemlock (early season) and thistle (mid-late season), with an average cover about 10%. By late October, blackberry cover within the treatment plots averaged 9%, with a range of 0% to 50% in measurement plots. An average of 74% of the measurement plots were stocked (i.e., had some blackberry cover); more than 60% of the plots had 5% of less cover. Height of the tallest cane averaged 5” (12.7 cm), with a range of 0” to 24” (0-61 cm) Three years post-treatment, the planted trees are free-to-grow, HB is a minor component, and the vegetative community is much more diverse, albeit still with a large component of exotic species.

Figure 7. July 2004. 4

th growing season.

Goat browsing treatment: Fenced plots of approximately 0.2 acres (0.08 ha) each were browsed by seven Angora goats intermittently from mid-May through early September. The goats were taken off the plots and moved to a nearby pasture when most (90%+) of the accessible browse in the plot had been consumed. The plots were mowed to stubble height at the end of the season. During the following April, two Boer (meat) goats were moved into each fenced plot and moved out in early June when most of the available browse was consumed. The goats were returned again for two weeks in late July. Results: During the first treatment season, goats browsed the blackberry heavily, removing nearly all of the accessible leaves and a significant portion of the succulent canes. However, woodier canes and leaves out of reach (above 4 ft or 1.2 m) were not consumed, and the browsed plants grew back rapidly. As a result, we mowed the browse plots at the end of the season, assuming that the goats would have an easier time controlling new sprouts. This proved to be the case. At the start of the second growing season, blackberry cover was 6 %. Following six weeks of continuous browsing, canes

Figure 6. Initial mowing with brush hog, spring 2000.

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were present essentially all leaves had been removed. After six weeks of regrowth, cover returned to about 30 %, with significant variation within the plots. The plots were browsed again for two weeks, reducing the blackberry cover to 16%. By the end of the season (late October), blackberry cover averaged 37%, with a range in the measurement plots of a trace to 100%. All of the plots had some cover; only 16% has 5% or less. Average height of the tallest can was 13” (33 cm), with a range of 1” to 28” (2.5 to 71 cm). Three years post-treatment, the browsed areas have returned to their pre-treatment stature, a 4'-6' high (1.2 to 1.8 m) HB thicket. Trial #2 - Methods tested: Manual/mechanical slashing of HB + spot herbicide treatment, intensive manual weeding Manual/mechanical slashing of HB + spot herbicide treatment (= cut + spot spray): The blackberry was cut by to stubble height in August by crews using chainsaws, brushcutters, and loppers. Most of the blackberry residue was windrowed at the outside edge of the plot pair. In early September, the windrows were chopped and masticated with a flail mower. Although the intention was to scatter the residue evenly across the plot pairs, this was not done. There was some resprouting of blackberry over the next 4-6 weeks. In early October, the sprouts were spot sprayed with Rodeo (glyphosate) mixed with an aquatic-labeled surfactant, LI-

700. The treated areas were planted in early November. The following April, a 3' (0.9 m) area around each planted tree was spot sprayed with Rodeo. In July, HB resprouts were cut and the cut surfaces immediately sprayed with Garlon 3A, using a hand sprayer. Intensive manual weeding (=multiple weedings): The site preparation treatment was identical to that of the cut + spot spray treatment described above, and the treated plots were also planted in early November. In the spring and summer following planting treatment plots were weeded using loppers, MacLeods, and other hand tools. Grass and other herbaceous weeds were grubbed, while the HB was cut or chopped at ground line. There was one weeding in March, two in April, two in May, two in June, and one each in July and August, for a total of 9. The intent was to maintain the treated areas in as weed-free a condition as possible throughout the growing season. Results: One year post-planting, HB cover in the cut + spot spray averaged 18% (range 1% - 39%); in the multiple hand cutting plots, it averaged 13% (range 2%-40%). The percentage of measurement plots in each treatment falling into three cover classes is shown in Table 1. Bare ground or mulch (primarily chopped blackberry canes) occupied 69% of the area in the multiple hand cutting plots and 64% of the area in the hand cutting + herbicide plots. The remainder of the area was occupied by a variety of grass and herbaceous species, including numerous exotic weeds. Table 1. Percentage of measurement plots in each cover class, by treatment

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Cover class (% HB cover)

Hand cutting + herbicide

Multiple hand cuttings

<10% 47% 53% 10%-40% 36% 36% >40% 17% 6% Average height of the tallest cane in the treatment plots was 4" (10 cm) (range 2”-12”, 5-30 cm) for the multiple weedings and 5" (12.5 cm) (range 2”-14”, 5-35 cm) for the cut + spot spray treatment. There was considerable variation in blackberry cover within and among plots in both treatments. Some plots in both treatments were HB free; others had substantial HB cover. Trial #3 – Methods tested: Slashing + herbicides, slashing + grubbing Slashing + herbicide treatment: Plots were cut in mid-summer to stubble height with hand tools (loppers, McLeods, etc); the residue was left in place. Following about 14 months of

regrowth, ½ of the plots were sprayed in early October with Roundup; the other ½ of were sprayed with Garlon 3A. The plots were cut to stubble height at the end of October and planted in mid-

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November. During the following April, a 3’ (0.9 m) area around each tree was sprayed with Roundup to control herbaceous competition. A 3’ (0.9 m) radius circle around each tree was manually weeded in July. Slashing + grubbing: Plots were cut in mid-summer to stubble height with hand tools (loppers, McLeods, etc.); the residue was left in place. This treatment was repeated one year later and again in late October of the same year. Trees were planted in November. In February and March of the following year, the plots were grubbed. In one plot, the entire area was grubbed to remove as many HB burls and roots as possible. In the other plots, an effort was made to Figure 9. Percent HB cover, by treatment and date _____________________________

grub all HB plants within 3' (0.9 m) of planted trees. Two foot (0.6 m) square mulch mats (Vispore mats) were then installed. In June, HB was cut to stubble height in a 4' (1.2 m) radius around each tree.

Results: Figure 1 shows the percent cover and average dominant height of HB in the treatment plots over time. In the slashing + herbicide treatment, the average cover in October 2002 was 72%, representing approximately 14 months of growth following the initial slashing to ground level. In May 2003, about 6 months after spraying, HB cover averaged 4% in the Roundup plots and 0% in the Garlon plots. In November 2003, average cover was 14% and 4% in the Roundup and Garlon plots respectively. In June 2004, about 19 months after spraying, average HB cover in Roundup plots had returned to 26%; it was 20% in the Garlon plots. However, one Roundup plots had much higher HB cover than all the others. Prior to treatment, the HB in this plots was visibly of lower vigor than that in other plots, probably due to moisture stress. Removing this plot, average cover in the

Roundup plots was 7% in June 2004 compared to 20% for the Garlon plots. The figures for average dominant height followed a similar pattern.

Percent HBB cover, by treatment and date

0

10

20

30

40

50

60

70

80

Mechanical totals Herbicide initial Roundup Roundup* Garlon

Treatment

HB

B P

erce

nt C

over

Oct '02May '03Nov '03June '04

For the slashing + grubbing treatment, average HB percent cover increased from less than 10 percent in October

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2002 to 60% in June 2004. Some plots in this treatment were entirely covered in HB to a height of 48" (123 cm) or more; in others, the distribution of HB was clumpy. The plot that was entirely grubbed had a lower HB cover but the ensuing soil disturbance resulted in a large "crop" of thistles and other weeds. Discussion: Mechanical/manual methods (mowing, slashing, etc.) Removing only the above-ground portion of the HB plant through mowing, hand slashing, and goat browsing, provided temporary reduction in cover but the HB plants grew back rapidly. If the goal in eliminate or substantially reduce HB from the site, these methods are ineffective. This result is no surprise. However, the temporary reductions in HB cover may be enough to establish native trees and shrubs. Because the HB can grow to 40" (102 cm) or more in one season and reach 6'-8' (1.8-2.4 m) within 2-4 years, desirable native vegetation is quickly overtopped until it reaches that height. Thus it will probably be necessary to re-treat areas for several years before the planted trees are free-to-grow. If plots are manually weeded very intensively (e.g., 6-10 times per season), they can be kept in a relatively weed-free state. In Trial #2 reported here, 9 weedings during the first season produced levels of HB control comparable to herbicides. Manual/mechanical treatments are expensive. Soll (2004) reports costs of up to $1,000 per acre ($2,500 per

hectare) for weed-eater clearing of dense thickets and more than $1,000 per acre for hand clearing of dense thickets. In the trials described here, the time needed for an initial clearing (site preparation) was 165-400 hours per acre (413 to 1000 hours per hectare) depending on conditions and crew capabilities, with 40-100 hours per acre (100 to 250 hours per hectare) needed for release work. For hand clearing HB thickets and release, a variety of tools were used, ranging from loppers and machetes to brushcutters and chainsaws. The most effective tool proved to be a chainsaw-style hedge trimmer. In several treatment plots in all three trials we observed that temporary reduction in HB cover helped release suppressed natural regeneration - either seedlings (primarily Oregon ash, Oregon white and black oak, and various shrubs) or root suckers (in the case of black cottonwood and willow). Growth of seedlings was slow and they appeared to be susceptible to overtopping by HB without further treatment, but the growth of the willows in particular was dramatic. Release of existing vegetation through reductions in blackberry cover may be a more cost-effective strategy than replanting in some cases. Mulch mats proved to be somewhat effective in preventing or at least delaying HB resprouting. During the first growing season, sprouts were observed to be pressing the undersides of the mats and a few emerged and grew upwards from the side. After a year the mats began to deteriorate and some sprouts grew up through holes in the matting. Though data are still be analyzed, it appears that the mulch mats provide at least a temporary reprieve

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from HB competition, as well as herbaceous and other weeds that compete with newly planted trees and shrubs. Mowing, slashing and related treatments typically produce a thick (2"-6") (5-15 cm) mulch of chopped up blackberry canes. This mulch appeared to suppress germination of many grass and broadleaf weeds, as well as conserve soil moisture. Areas where mineral soil was exposed had more weeds, especially plots that were grubbed. Goat browsing In some circles, goats are in vogue as a weed control tool. Our experience was that goats were ineffective for site preparation in HB. They were more successful in browsing back the HB re-sprouts after the clumps were mechanically treated, as they kept cover of new canes and foliage to low levels while present in the plots. However, as soon as the goats were removed, the HB grew back rapidly. An obvious problem with goats is that as non-selective browsers, they will eat any woody vegetation present, including desirable native trees and shrubs. In another SW trial, 3-4 years of intermittent goat browsing, with supplemental hand weeding, appeared to provide good control of HB near a stream. In conclusion, goats are probably best suited for HB control when: 1. There is an initial mechanical

treatment so the goats can browse the re-sprouting canes and leaves;

2. The goats are allowed to browse over the entire growing season;

3. This process is continued for two or more growing seasons;

4. Supplemental mechanical / manual treatments are used;

5. Browsing of other desirable woody vegetation in the area can be adequately controlled or is not an issue; and

6. Fencing, access to water, predation, and other management issues can be addressed.

Mechanical + herbicides In all the plots were herbicides were used, an initial mechanical or manual treatment was needed to remove the above ground portions of the HB plant. This treatment as noted above produced a relatively thick mulch that appeared to suppress growth of grass and some broadleaf weeds. Resprouting HB plants were then spot sprayed. In most cases a backpack sprayer was used for spot foliar applications. In Trial #2, a hand sprayer was used for a cut surface treatment using Garlon 3A. The herbicide treatment was more effective than manual or mechanical treatments, measured in terms of HB percent cover and average dominant height. Herbicides did not eliminate all HB but substantially reduced its cover. In general, the herbicide-treated plots had a larger number of species (albeit many of these were exotics) than the mechanical/manual plots, most of which were still dominated by HB. The timing of the herbicide application was important. Spring and early summer applications of Roundup (which were done primarily to control herbaceous weeds) had little effect on HB, but fall applications were much more effective. The time window for Garlon appears to be wider, though the fall application appeared to be more effective. Plant vigor is also important. Control was very poor in the one Roundup plot in Trial #3 where the HB

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plants appeared to be moisture stressed at the time of treatment. In addition, enough time needs to elapse between cutting and spraying for the resprouts to become sufficiently large, at least 18" (46 cm) according to Soll (2004). In Trial #2, Rodeo was applied only about 6 weeks after cutting in late August. This was not enough time for the canes to reach this size, and many canes had not yet resprouted. As a result, the treatment was not effective. Overall, Roundup appeared to be more effective than Garlon in killing HB plants and reducing re-sprouting when applied optimally. Volatility in high temperatures is a concern with herbicide applications in southwestern Oregon, where maximum daytime temperatures often exceed 80 degrees F (27 C) from late Spring through mid-fall. The herbicides of greatest concern in this respect are Garlon 4 (the ester formulation of triclopyr) and Crossbow, a commonly used weed-killer that contains Garlon 4 and 2,4,d. Volatility is less an issue with glyphosate and Garlon 3A. Use of herbicides in riparian areas commonly raises concerns about deleterious effects on aquatic organisms, water quality, etc. As of this writing, the Garlon 4 formulation cannot be used within 100' (30 m) of salmon-bearing streams in the Pacific Northwest. Specific regulations pertaining to use of herbicides vary by state and land use. For example, under Oregon's Forest Practices Rules, backpack spraying is allowed within 10' (3 m) of perennial streams but no-spray buffer for aerial applications are much wider. Consult State Departments of Agriculture and

Forestry for more specific information. In all cases, herbicide users must read and follow the instructions on the manufacturer's label, i.e., the label is the law. In all cases, extreme care should be taken to avoid spray drift. Spot and cut surface treatments reduce this potential. The Rodeo formulation of glyphosate with LI-700 as a surfactant is labeled for aquatic use and is probably the lowest risk option for near-stream herbicide use; consult the label and state regulatory authorities for more information. The Pacific Northwest Weed Control Handbook, updated annually, contains detailed information about herbicide effectiveness, rates, and timing. OTHER HB CONTROL METHODS Removal of roots & burls Removal of HB roots and burls can be an effective control method, but is difficult for several reasons. First, since new plants can resprout from root fragments, all or nearly all of the underground portion of the plant must be removed. Second, since roots and burls frequently lie 12” or deeper within the soil, and form a dense network, a substantial amount of soil must be disturbed in the process of their removal. This raises concerns for erosion and sedimentation, especially on slopes or near streams. Soil disturbance also provides idea conditions for invasion by weeds, both from off the site and from the soil seed bank. Third, manual removal is extremely labor intensive. Though not quantified in our SW OR field trials, Soll (2004) gives a range of 300-1000 hours per acre (750 to 2,500 hours per hectare) depending on

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conditions and crew capabilities. Livingtson (2004) reported costs of $3,500/acre for a thorough manual grubbing that appeared to provide good to excellent control of HB on a site near the Little Applegate river. Fire Fire temporarily removes the aboveground portion of the plant while leaving the root crown and rhizomes unaffected. HB sprouts were observed within 10 days of one mid-summer fire in SW Oregon. Edge effects With all approaches to HB control, a challenge is the potential for invasion of treated areas from surrounded untreated HB thickets. Even when HB has been effectively controlled in a given area, it may be rapidly invaded from surrounding HB patches. Shade HB is considered shade-intolerant. In practice, most narrow riparian buffers with deciduous trees have adequate sunlight, from above and from the side, to sustain vigorous HB growth. Establishing wider buffers with a heavy conifer component may provide enough shading to achieve long-term control. Summary Recommendations for HB control • Good to excellent HB control can be

achieved in many cases with an initial mid-summer cutting or mowing followed by a herbicide treatment once the HB has regrown to boot height. Garlon 3A and Roundup are both fairly effective; Rodeo (the aquatic labeled version of Roundup) should produce similar

results and with an aquatic surfactant such as LI-700, risk to aquatic resources is minimal. Spot (as opposed to broadcast) treatments minimize the risk of drift; a cut surface treatment is even more selective but is very labor intensive. The initial treatment is unlikely to eliminate all HB plants; followup treatments will probably be needed.

• Repeated cuttings or mowings are unlikely to provide substantial long-term reductions in HB cover but can provide enough of a temporary reduction in cover to allow desirable plants to become established. An initial mowing or cutting to stubble height, followed by planting, installation of mulch mats, and a minimum of two release cuttings per year appears to be feasible strategy, but release treatments will need to be continued for several years until the planted trees or shrubs are free to grow. Thus, this approach seems best suited for relatively small areas, situations where landowners or others involved in the project are strongly committed to follow-up, and where budgets or volunteer labor pools are adequate. .

• Grubbing or mechanical removal of

roots and burls is effective if done thoroughly. Concerns are soil disturbance and erosion potential, the likelihood of weed invasion, and cost.

• Release of existing natural

regeneration of native riparian trees and shrubs (especially from stump sprouts or root suckers) can be achieved with temporary reductions in blackberry cover. This is particularly true where soil moisture

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is not limiting, for example, close to the active stream channel.

Integrated Strategies for HB Control and Restoration of Desirable Riparian Vegetation • Release existing natural regeneration

by mechanically controlling blackberry where feasible. This can be a simple as cutting back HB encroaching on clumps of willows or other desirable plants.

• Promote natural regeneration of

desirable trees and shrubs, both from seed and vegetatively, by maintaining HB cover at low levels. This probably requires, at minimum, two cuttings per year. Once natural regeneration is visible, crews must recognize it and not cut it – a very practical challenge.

• Recognize that repeated treatments

will be needed to establish desirable vegetation communities. Persistence is essential.

• Consider judicious use of herbicides following a mechanical treatment as a cost-effective method of HB control. Use of aquatic-labeled herbicides and surfactants (e.g., Rodeo and LI-700), with spot or cut surface treatments, minimizes the risk to other organisms.

• Use large planting stock, good weed

control, and, where feasible, supplemental watering, to promote high survival rates and rapid growth of planted native trees and shrubs.

• Consider long-term control strategies

such as planting conifer buffers on the outside of riparian zones, e.g., droughty upper terraces, to provide denser shade, as well as other benefits (e.g., source of large wood over time).

References Cited Amor, R.L. 1972. A study of the ecology and control of blackberry (Rubus fruticosus L. agg.). J. Australian Inst. Agric. Sci. 38(4): 294 Bridges, A. 1996. Solving Blackberry Problems. Journal of Pesticide Reform, 16(3):23 Dellow, J. J. 1988. Large area blackberry (Rubus fruticosus agg.) control using grazing goats. Plant Protection Quarterly Vol. 32(2):83-84.

Department of Environment and Heritage [Australia]. 2004. Blackberry (Rubus fruticosus aggregate). Weeds of National Significance, Weed Management Guide. Available at: http://www.deh.gov.au/biodiversity/invasive/weeds/r-fruticosus.html DiTomaso, J. M. 1997. Wild Blackberries. UC Pest Management Guidelines. UC DANR Publication 7434. Gregory, S. 1999. Summary of Current Status and Health of Oregon's Riparian Areas. In: Chapter III, Health of Natural Systems and Resources, Oregon State of


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the Environment Report 2000. Oregon Progress Board. Hibbs, D. and A. Bower. 2001. Riparian forests in the Oregon Coast Range. Forest Ecology and Management 154 (2001) 201-213. Hoshovsky, M. 1989. The Nature Conservancy Element Stewardship Abstract for Rubus discolor, (Rubus procerus). Available: http://tncweeds.ucdavis.edu/esadocs/documnts/rubudis.html Howe W, and F. Knopf. 1991. On the Imminent Decline of Rio Grande Cottonwoods in Central New Mexico. The Southwestern Naturalist 36(2):218-224. Lesica P. and S. Miles. 1999. Russian olive invasion into cottonwood forests along a regulated river in north-central Montana. Canadian Journal of Botany 77: 1077-1083. Massingill, C. 2003. Coastal Oregon Riparian Silviculture Guide. Charleston, Oregon. Coos Watershed Association. Livingston, David. 2004. Personal Communication. Tour of selected Applegate Watershed Council riparian projects. Soll, J. 2004. Controlling Himalayan Blackberry (Rubus armeniacus [R. discolor, R. procerus]) in the Pacific Northwest. The Nature Conservancy. Available at: http://tncweeds.ucdavis.edu/moredocs/rubdis01.pdf

Tirmenstein, D. 1989. Rubus discolor. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [2004, July 1].

management of himalayan blackberry in sw oregon

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