Several are even compatible, to a degree atleast, with biological control programs, andentomologists are happy to be seeing a lotmore interest from growers in that area.Most of these new miticides have relativelyshort re-entry intervals and good plantsafety records.

If all this sounds too good to be true, it’sbecause we’re not quite finished. The firstcomment I usually hear from growers relatesto sticker shock: no longer are we seeing $8per 100 gal. of dilute spray; $20-80 for low

The greenhouse environment isnot only nearly ideal forgrowing plants; it can pro-duce outstanding pest infesta-tions, as you surely have dis-

covered. Mites seem to be one of the greatlevelers among growers, common to manygreenhouse crops and production systemsaround the world. They are most notoriousin long-term, protected growing situationssuch as greenhouse tomatoes, stock plants orcut flowers but are also often seen at homeon bedding plants and even happily attackplugs, although they rarely have sufficientopportunity to do so.

About 10 years ago, the situation forgreenhouse mite control was looking ratherbleak, with just a few dwindling optionsavailable such as Pentac and Kelthane, sev-eral pyrethroids, Thiodan, diazinon andinsecticidal soap. Some of these productshave been phased out (Pentac and diazi-non/Knox-Out, for example) and the futureof others is in question.

Today, the situation is dramatically dif-ferent. The good news is that more than 15miticides are now available for greenhouseuse, with no small credit due to the indus-try in Japan, where mites are apparentlyimportant pests. Most of the chemicals havedifferent modes of action, and did I forgetto mention that many are quite effective?

Managing Mites

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Spider mitesTwo spotted spider mite Tetranychus urticae

Carmine spider mite Tetranychus cinnabarinus

Lewis spider mite Eotetranychus lewisi

Acarid mitesBulb mite Rhizoglyphus robini,

Rhizoglyphus echinops

Tarsonemid mitesBroad mite Polyphagotarsonemus latus

Cyclamen mite Phytonemus pallidus

Eriophyid mitesPurple or ribbed tea mite Calacarus carinatus

Fuchsia gall mite Aculops fuchsiae

Gardenia bud mite Colomerus gardeniella

Tomato russet mite Aculops lycopersici

Figure 1. Some of the main mites on greenhouse crops. Forinformation on various mites, go to http://mrec.ifas.ufl.edu/lso/.

Top right: Bulb mite; Above: Bulb mite injury (tunneling)in stem of Easter lily. (Photos courtesy of Daniel Gilrein)

By Daniel Gilrein

With so many miticide choices, which product do you use and when do you use it?

application rates is more typical. Despitethis new reality, I strongly recommend thatgrowers do not base miticide selection onprice alone, since many of these newer prod-ucts are long-residual (weeks of activity forsome). Other changes with miticides includerestrictions on numbers of applications percrop, similar modes of action and fewerbroad spectrum products. So, when there isa mite problem, 15 choices and all these newconsiderations, which product do you use?

SELECTION GUIDELINESThe first step in choosing a miticide is to

determine what kind of mite problem youhave; local or state diagnostic labs can help.Next, assess the severity: Is there a need forimmediate knock down or are mite levelsstill low and early in the infestation, whencertain materials work very well? A handlens is useful here. Finally, consider cropsensitivity and application history (miticidesused previously on the crop). This shouldwhittle down the list to a few choices whereother considerations (Is contact activity suf-ficient or is translaminar activity needed?Will residue be an issue? Is this also to beused in landscapes? Is compatibility withbiological control important?) plus price canguide the selection.

TWOSPOTTED SPIDER MITEFor the most part, when we think of mites,

the usual suspect is twospotted spider mite,sometimes known as red spider. This namerefers to the red-orange color female mitesdevelop during short-day conditions (lessthan about 13 hours). Usually, these mites area pale yellowish or whitish color with twoindistinct dark green spots on either side ofthe abdomen. They spend most of their timeunder leaves and prefer protected areas alongveins or in concave hollows. They are quitesmall, only about 0.02 inches long, not easilynoticed until sufficient numbers have causedobvious damage. During warm conditions(90° F) the time from egg to adult is onlythree and a half days, and under such condi-tions, populations explode.

Twospotted spider mite has a very widehost range — perhaps hundreds of differentplants, including many weeds. They can overwinter on plants and debris outdoors or inprotected greenhouses, so cleaning up weedsand washing house benches and structuresshould be a priority where sensitive crops aregrown. Early symptoms include a pale fleck-ing or stippling, yellowish blotches and somedistortion of young growth. When numbers ç

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MITE(S)PRODUCT CONTROLLED REI* NOTES

Apply early in infestation

Hexygon Spider mites 12 Do not rotate with Ovation. Apply only once per crop cycle (Gowan Company) or per year for crop cycles longer than one year.

Ovation Spider mites 12 Do not rotate with Hexygon. Bright color may be noticeable (Scotts Company) on light flowers and foliage. Apply only once per crop cycle.

Sanmite Spider, broad mites 12 Do not rotate with Akari. Helps control whitefly. (Scotts Company) Apply only once per season.

TetraSan Spider mites 12 Translaminar activity. Apply no more than twice per (Valent USA) cropping cycle or per six months.

For quicker knock down

Akari Spider mites 12 EPA designated “reduced-risk.” Do not rotate with Sanmite. (SePRO) Do not apply more than twice per crop or growing

season, or in succession.

Pylon Spider, tarsonemid, 12 Translaminar activity. Not highly effective against Lewis (Olympic) eriophyid mites mites. Note plant sensitivity precautions. Do not apply

twice in succession to the same crop or three times during a growing cycle. See other resistance-management information on label.

Avid Spider, tarsonemid, 12 Translaminar activity. Some ferns and shasta daisy are (Syngenta) eriophyid mites sensitive. Note resistance-management recommendations.

Floramite Spider mites 4 EPA designated “reduced-risk.” Adjust water to below (Crompton/Uniroyal) pH 7 and add conditioner if hardness levels are high.

Do not make successive applications or more than two applications per crop per year.

Kelthane Spider, tarsonemid, 48 Maximum two applications per crop or season. 50WSP (Dow AgroSciences) eriophyid mites formulation is currently registered.

Vendex T/N/O Spider mites 48 Restricted-use. Test first before large-scale use. (Griffin LLC) Do not mix with oil or apply to poinsettias or

chrysanthemums in bloom. Temperatures should be over 70º F for best results.

Thiodan, Thionex Cyclamen, tomato 24 Restricted use. Both EC and WP formulations available; (FMC, Makhteshim) russet mites use WP on sensitive crops.

Pyrethroids Spider mites 12-24 Includes Tame, Talstar GH, Mavrik, Scimitar. Broad mite also on Scimitar and Talstar labels. Some products may be restricted-use. See labels for other restrictions.

Short-residual activity

Insecticidal soap; M-Pede Spider mites 12 Test before large-scale use. Note plant sensitivity (Dow AgroSciences) precautions.

Ultra-Fine Oil Spider mites 4 See list of labeled crops. Note label cautions on frequency and environmental conditions during application. Test before large-scale use.

Triact 70 “Mites” 4 Test before large-scale use. Note plant safety cautions. (Olympic)

Hexacide “Mites” 1 “Minimum-risk” product (no EPA registration required). (EcoIPM) Test before large-scale use. “Meets requirements for

National Organic Program.”

GC-Mite Spider, rust “Minimum-risk” product (no EPA registration required). (JH Biotech) (eriophyid) Test before large-scale use. OMRI-listed (for organic

growers). Buffer water to pH 3.5 - 7.5.

NOTE: Before using any product on a large scale, be sure products are registered in your state, read labels carefully and test for phyto-toxicity on a representative portion of the crop. *REI = Re-entry interval (in hours)

Figure 2. Sample list of miticides for greenhouse production.

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pests & diseases

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build to very high levels there may be webbing and mites clustering athigh points in an attempt to disperse; plants may even be killed.

OTHER SPIDER MITESCarmine spider mite. It looks somewhat like a dark red version of

twospotted spider mite and was found on zonal geraniums submit-ted to our diagnostic lab. We suspect they may have been at leastpartly to blame for some brown spotting and yellow blotches onlower leaves. There was also light edema evident.

Lewis mite. Lewis mite has been a problem in the last few years onpoinsettias. Under magnification, they slightly resemble twospottedspider mite but are somewhat smaller, narrower and have severalsmall dark green spots instead of just two. Lewis mites only seem tolike a few kinds of plants. There was a recent report on zonal gerani-ums. We found they could indeed survive for a time on some ivy andzonal cultivars, but the damage was extremely light and infestationsdid not persist. On poinsettia, injury appears as an extremely finespeckling or stippling, giving an overall appearance of nitrogen defi-ciency. Unfortunately, by the time damage is apparent the mite num-bers are already quite high. I recently spoke with a grower whonoticed a group of poinsettias lighter in color than the surroundingplants but did not investigate until webbing and brown spots werestarting to appear. The decision at that point was to discard the worstof the lot, which is sometimes the best strategy. ç

pests & diseases

Top: A comparison of poinsettias, healthy (left) and damaged (right), by Lewis spider mite;Bottom: View of Salvia farinacea showing typical injury from broad mite (stunting andcurling of foliage), side view.

BROAD/CYCLAMEN MITESIn the last few years, I have received more plant samples infested

with broad or cyclamen mites than throughout the previous 12 years.Clearly these tarsonemid mites are becoming more of a problem. Themost likely explanation is that tarsonemid mites are more typically asso-ciated with vegetatively propagated material than seed-grown crops.

Broad and cyclamen mites are not spider mites and are not necessarilycontrolled with the same materials used for spider mites, although thereare some exceptions. They have a fairly wide host range, including manycommon greenhouse crops such as cyclamen, gerbera, begonia and impa-tiens. I have seen broad mite cause a russeting or fine flecking on NewGuinea impatiens flowers and stems. Last year Salvia farinacea seemed tobe a favorite target for broad mite. Young leaves took on a gray-green castwith downward curling and stunting. On African violet, cyclamen miteinjury closely resembles that caused by foliar nematode. Typical damageis stunting or distorted young leaves, though larger buds or the growingpoint may even be killed.

These mites are extremely tiny, and we use high-power magnifica-tion to detect them, prying apart the smallest leaves to look for them.Under conditions of high humidity, they can also be found on olderleaves. Sometimes, the mites themselves are hard to find, especially ifsome kinds of miticides have already been applied. We have been ableto confirm broad mite infestation in such cases by locating eggs or theirremnants, which have distinctive hobnail ornamentation.Unfortunately, early signs of infestation are not obvious. In severalcases, growers were quite surprised how suddenly the damage becameapparent, naturally coinciding with the busy spring shipping season.

BULB MITESAlready this spring I have had the first inquiry concerning bulb

mite on Easter lily. With the decline in methyl bromide soil treatmentit might be a good idea to stay alert for signs of this problem,although it has fortunately not been common. Infestations are proba-bly brought on by bruising or damage of bulb scales, including thatcaused by fungus gnat larvae. I have also found bulb mites on gladi-olus corms and tulip bulbs, and they have been reported on a varietyof other bulbs and roots, including dahlia tubers.

Injury might be first apparent above ground as a yellowing ordecline of the plant due to the damage below. The bulb, corm ortuber will show rotten areas or portions of scales excavated by mite

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Zonal geranium leaf underside showing symptoms we associate with twospotted spidermite injury.

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activity. I have even seen bulb mitesmoving upward in Easter lily stem pith,leaving a brown trail of hollow dead tis-sue as they went.

According to older fact sheets andreports, Kelthane bulb dip was the stan-dard treatment, although labels nolonger allow this use because it wasmessy and growers wondered what todo with the leftover dirty pesticide sus-pension. At the present time, it appearsthe only possible treatment for post-planting suppression may be a drenchwith DuraGuard (Whitmire Micro-Gen),which allows such use for a broad rangeof soil-borne organisms (check with localauthorities for latest options).

LESSER KNOWN MITESIt has been many years since I have

encountered some of the following lesser-known eriophyid mites on any green-house crop. These mites rival tarsonemidsin small size and can cause some unusualplant symptoms, depending on the mitespecies, that can easily be mistaken for aplant disease.

Fuchsia gall mite is sometimes a pest ingreenhouse crops but more often in outdoorlandscape plantings in the coastal westernUnited States. The most common symptonof Fuchsia gall mite is a distortion andstunting of terminal growth. Apparently,

hummingbirds are implicated in the out-door spread of this pest. Some work isbeing done on breeding mite resistance intohybrid fuchsias for landscape use.

Tomato russet mite, causing yellowing orcurling of foliage, is an occasional problemin greenhouse tomato production. It alsofeeds on related plants such as nightshadeand petunia and probably survives liketwospotted spider mite in unheated green-houses over the winter.

The last of the eriophyids is purple teamites. They have caused recent concern inspathiphyllum crops, causing a bronzingbetween veins on leaves. There areundoubtedly other eriophyids we willfind on greenhouse crops, especially asthe popularity of vegetatively producedmaterial increases.

Daniel Gilrein is extension entomologist atCornell Cooperative Extension of SuffolkCounty, Riverhead, N.Y. He can be reachedby phone at (631) 727-3595 or E-mail atdog1@cornell.edu.

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