Velvety green with faint yellow longitudinal stripes and many fine hairs; up to 1 and 1/4 inches long.
Common Host Plant(s)
Cabbage, cauliflower, collards, Brussels sprouts, mustard, turnip and kale.
Feeds on underside of leaves, producing ragged holes; bores into heads.
Throughout United States.
Imported cabbageworms overwinter in plant debris as pupae. The time span from egg to adult moth is about four to five weeks. Multiple generations occur annually in Virginia.
Since several pests appear simultaneously on crucifers, all must be considered when applying thresholds. Therefore, the following thresholds take into account the combined levels of the following cole crop caterpillar pests: 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, see table below.
|Fresh Market Cabbage|
|Treatment advised if:|
|Seedbed||10% or more plants infested|
|Transplant to cupping stage||30% or more plants infested|
|Cupping to early heading||20% or more plants infested|
|Early heading to mature||10% or more plants infested|
|Fresh Market Broccoli and Cauliflower|
|Treatment advised if:|
|Seed bed||10% or more plants infested|
|Transplant to first flower||50% or more plants infested|
|Flowering to mature head||10% or more plants infested|
Handpick caterpillars where found. Conduct thorough postharvest cleanup in gardens where the imported cabbageworm has been a problem in the previous year.
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 parasitic wasp, Trichogramma sp., attacks imported cabbageworm eggs; mass releases of Trichogramma sp. may be successful in reducing pest populations. Several other parasites attack pupae and larvae of the imported cabbageworm. The braconid wasp Apanteles glomeratus is most effective. The imported cabbageworm is also susceptible to attack by generalist predators such as stinkbugs and Polistes sp. wasps. Natural control by viruses and bacterial diseases occurs as well.
Treat with a registered insecticide every 4 days after first true leaves appear until harvest if worms are still present. Direct insecticides to the undersides of leaves.
Foster, Rick and Brian Flood. 1995. Vegetable Insect Management, Meister Publishing Company, Willoughby, Ohio. pp. 104-107.
Virginia Cooperative Extension materials are available for public use, reprint, or citation without further permission, provided the use includes credit to the author and to Virginia Cooperative Extension, Virginia Tech, and Virginia State University.
Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Edwin J. Jones, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; M. Ray McKinnie, Administrator, 1890 Extension Program, Virginia State University, Petersburg.
April 25, 2011