details

Description

Adult Description:The adult butterfly has a wingspan of 1-1/2 inches. The forewings are black-tipped. A female has two black spots on top of each of her forewings; a male has only one spot. Hind wings are all white on the surface except for a black spot. There is a slight yellowish hue on the undersides of the wings. Each adult female lays hundreds of eggs.

Larva Description: The larvae are bright green caterpillars that feed on the leaves of the crops. There is also a yellow stripe that runs down the full length of the caterpillar.

Host Plant:Broccoli, Brussels sprouts, cabbage, cauliflower, Chinese broccoli, Chinese cabbage, choy sum, collards, daikon, horseradish, kale, kohlrabi, mustard, mustard cabbage, radish and turnip.

Ecological Threat

All the vegetables of the cabbage and mustard families are hosts of the imported cabbageworm. With such a diverse plant appetite, the cabbage worm is a dangerous invasive species.

Biology

The life span from egg to adult takes from 4 1/2 to 7 weeks depending on temperature. In temperate regions there are three to five overlapping generations per year. In Hawaii this pest is found throughout the year. Eggs and larvae of this insect do not develop at temperatures below 50^oF and larvae do not develop at temperatures above 90^oF

History

Imported cabbageworms are very common to all parts of the United States and Canada. Introduced into the New World in 1860 from Europe, within 20 years it spread throughout the entire eastern United States. This pest was first recorded in the State on Oahu in 1897 and is now common throughout all islands.

Native Origin

Europe, North Africa and Asia

Current Location

Since the Cabbage White Butterfly was introduced over 150 years ago, this insect has had plenty of time to distribute all over the United States

Potentially all states except Alaska

Management

High temperatures can inhibit larval development and heavy rainfall can cause high mortality in early instars. Therefore, larval populations are small during hot and wet seasons, and large in dry and cool seasons. In the northern United States, there are no native egg parasitoids that attack these pests, and over the past 30 years there have been several attempts to find a suitable species and strain of Trichogramma for this use. There are three pre-adult periods where extensive mortality may occur: 1) between hatching and the second molt, 2) larval stages three to five and 3) during the pupal stage. Control is most effective when it is directed towards the young to half-grown. During these stages the worms are more susceptible to control measures and damage is still relatively low. Serious infections can be somewhat controlled with Bt (Bacillus thuriengensis) a bacteria that is poisonous to the moth larvae

References

Ashby, J. W., & Pottinger, R. P. 1974. Natural regulation of Pieris rapae Linnaeus (Lepidoptera: Pieridae) in Canterbury, New Zealand. New Zealand journal of agricultural research, 17(2), 229-239.

Harcourt, D. G. 1966. Major Factors in the Survival of the Immature Stages of Pieris rapae (L.). Can. Entomologist. 98(6):653-662.

Luther, G. C., Valenzuela, H. R., & Defrank, J. 1996. Impact of cruciferous trap crops on lepidopteran pests of cabbage in Hawaii. Environmental Entomology, 25(1):39-47.

Oatman, E. R., G. R. Platner, and P. D. Greany. 1968. Parasitization of imported cabbageworm
and cabbage looper eggs on cabbage in southern California, with notes on the colonization of Trichogramma evanescens. Journal of Economic Entomology 61:724-730.

Parker, F. D. and R. E. Pinnell. 1972. Effectiveness of Trichogramma spp. in parasitizing eggs of
Pieris rapae and Trichoplusia ni. 1. Field studies. Environmental Entomology 1:785-789.

Scudder, S.H. 1887. The introduction and spread of Pieris rapae in North America, 1860-1886. Memoirs of the Boston Society of Natural History 4(3):53–69.

http://www.itis.gov

http://usda.gov

http://www.bugguide.net

http://en.wikipedia.org (for picture only)