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United States Department of Agriculture

Agricultural Research Service

Title: Parasitism by Diadegma Insulare (Hymenoptera:ichnuemonidae) in Collard in South Carolina

Authors
item Mccutcheon, Gloria - CLEMSON UNIVERSITY
item Simmons, Alvin
item Gourdine, J - CLEMSON UNIVERSITY

Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 15, 2004
Publication Date: October 1, 2004
Citation: Mccutcheon, G.S., Simmons, A.M., Gourdine, J.S. 2004. Parasitism by diadegma insulare (hymenoptera:ichnuemonidae) in collard in south carolina. Journal of Entomological Science. 39:673-676.

Interpretive Summary: The diamondback moth is a global pest of crucifer crops, including collard and cabbage. Diadegma insulare is a small wasp which is a parasite of the caterpillar stage of the diamondback moth. The wasp parasitizes and kills the pest before the pest becomes an adult. Wildflowers in and around crops have been shown to increase the abundance and rate of attack by some parasites. This is because the flowers can serve as a nectar food source for these beneficial wasps. A study was conducted to determine any difference in the seasonal abundance of the diamondback moth and parasite in collards with and without wild nectar-producing plants around the borders of fields. Also, data were collected on the abundance of the parasite in two geographical regions in South Carolina. No effect by the wildflowers was observed during the growing season, although it was difficult to keep the check plots free of weeds. Parasitism was greatest during March to May when about 70% of the pests were killed by the wasps. Seasonal abundance of the pest was higher during the spring than during late August. Parasitism was higher at the coastal site (Charleston County) than at the mid-state site (Lexington, County). In areas such as Lexington County, where collards are grown year-round, the data suggest that natural populations of parasites alone may not be sufficient to manage the diamondback moth.

Technical Abstract: Diadegma insulare (Cresson) (Hymenoptera: Ichneumonidae) is a major natural enemy of larvae of the diamondback moth, Plutella xylostella (L.). The diamondback moth is a global pest of crucifer crops, including collard and cabbage. Wildflowers in and around crops have been shown to increase the abundance and rate of parasitism. This is because the flowers can serve as a nectar food source for these parasitoids. A study was conducted to determine any difference in the seasonal abundance of P. xylostella and D. insulare in collards with and without wild nectar-producing plants around the borders of fields. Also, data were collected on the abundance of the parasitoid in two geographical regions in South Carolina. No effect of wildflower was observed during the growing season, although it was difficult to keep the check plots free of weeds. Parasitism was greatest, up to 70%, during March to May in Charleston County. Seasonal abundance of the pest was higher during the spring than during late August. Parasitism was higher at the coastal site (Charleston County) than at the mid-state site (Lexington County). In areas such as Lexington County, where collards are grown year-round, the data suggest that natural populations of parasitoids alone may not be sufficient to manage P. xylostella.

Last Modified: 4/16/2014
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