Larva: Pale green with black hairs; up to 1/3 inch long when mature. The body is slender and tapered at both ends, with a distinctive "V" formed by two prolegs at the rear end. It wriggles rapidly when disturbed and often drops from the plant and hangs by a silken thread.
Cabbage, broccoli, cauliflower, kale and brussels sprouts.
Larva eats small holes in leaves and buds. Adult (diamondback moth) does no damage.
Throughout United States.
Adult moths lay minute eggs in groups of less than three, or singly, on the underside of cole crop leaves. In about 10 to 14 days tiny larvae hatch, bore into leaves, and feed internally on leaf tissue. Larvae emerge and begin feeding on outer leaf tissue in 10 to 30 days, depending on environmental conditions. Larvae spin a loosely woven cocoon, which resembles gauze, on plant leaves or stalks and pupate. The lifecycle from egg to adult moth occurs in 3-4 weeks. Adult moths may overwinter in cabbage debris during mild winters, but diamondback moths are generally introduced to fields through infested transplants or by migration from the south. Multiple, overlapping generations occur annually in Virginia.
Since several pests appear simultaneously on crucifers, all must be considered when applying thresholds. Therefore, the following thresholds concern levels of four cole crop caterpillar pests combined: diamondback moth, imported cabbageworm, cross-striped cabbageworm, and cabbage looper. These thresholds are for fresh market quality cabbage, broccoli, and cauliflower; if more damage is economically acceptable, a 75% infestation may be tolerated before treating plants.
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treatment advised if: |
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seedbed |
10% or more plants infested |
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transplant to cupping stage |
30% or more plants infested |
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cupping to early heading |
20% or more plants infested |
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early heading to mature |
10% or more plants infested |
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treatment advised if: |
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seed bed |
10% or more plants infested |
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transplant to first flower |
50% or more plants infested |
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flowering to mature head |
10% or more plants infested |
Plow under crop debris and destroy mustard type weeds several weeks before planting.
Bacillus thuringiensis, or Bt, (Bactur, Dipel, SOK-BT, Thuricide) 2.0 to 3.0 tbsp in 1 gallon water. It is not necessary to wait before harvesting after an application of Bt.
A small, parasitic wasp, Horogenes insularis (Cresson) attacks the this pest and has been recorded as parasitizing as many as 95% of the diamondback moths in a population.
Horogenes plutellae (Viereck) and Diadromus plutellae (Ashmead) also parasitize diamondback larvae.
Treat with a registered insecticide every 4 days after first true leaves appear until harvest if worms are still present. Direct insecticide to the undersides of leaves.
Notice: Because pesticide labels can change rapidly, you should read the label directions carefully before buying and using any pesticides. Regardless of the information provided here, you should always follow the latest product label when using any pesticide. If you have any doubt, please contact your local Extension agent or pesticide dealer for the latest information on pesticide label changes.
Disclaimer: Commercial products named on this site are for informational purposes only. Virginia Cooperative Extension does not endorse these products and does not intend discrimination against other products which also may be suitable.
Foster, Rick and Brian Flood. 1995. Vegetable Insect Management, Meister Publishing Company, Willoughby, Ohio. pp. 104-107.
http://www.ipm.ucdavis.edu/PMG/r108301311.html