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United States Department of Agriculture

Agricultural Research Service

Title: Evaluation of Rearing Methods for Diadegma Insulare (Hymenoptera: Ichneumonidae), and Endoparasitoid of the Diamondback Moth (Lepidoptera: Plutellidae)

Authors
item Sieglaff, D. - ENT DEPT., UNIV OF FL
item Mitchell, Everett
item Hu, G. - ENT DEPT., UNIV OF FL

Submitted to: Florida Entomologist
Publication Type: Research Notes
Publication Acceptance Date: June 15, 1998
Publication Date: N/A

Interpretive Summary: The diamondback moth is the most important insect pest of cruciferous plants worldwide. The diamondback moth typically has been controlled by using synthetic insecticides, but resistance to virtually all commonly used insecticides has forced development of IPM programs for this pest. The augmentative release of natural enemies can be an important component in many IPM programs, and parasitoids are considered essential to management programs for diamondback moth. The larval endoparasitoid Diadegma insulare is a very important natural enemy of diamondback moth, but wasp populations generally lag behind pest numbers in the field. Scientists at the Center for Medical, Agricultural, and Veterinary Entomology, Gainesville, FL, are developing methods for rearing this parasitic wasp on artificial media in numbers that can be used to supplement naturally-occurring D. insulare populations. Present rearing procedures require that host diamondback moth larvae be hand-placed on a natural food source, typically collard leaves. Experiments showed that D. insulare can be reared successfully on diamondback moth-infested artificial diet cakes treated with a water extract of collard leaves. Parasitism increased from 19% on the artificial diet without the chemical stimulant to 46% on diet treated with collard extract. Results also showed that the wasps were more proficient at stinging larvae, and the sex ratio of wasps produced was more like field populations when left confined with larvae for 48 h.

Technical Abstract: The augmentative release of natural enemies can be an important component in IPM programs, and parasitoids are considered essential to any IPM program for management of diamondback moth, Plutella xylostella (L.), in cabbage and other cruciferous crops. The larval parasitoid Diadegma insulare (Cresson) is a very important natural enemy of diamondback moth. Methods were developed for rearing this parasitic wasp in the laboratory on artificial media in numbers that can be used to supplement naturally-occurring populations in IPM programs. D. insulare were reared on diamondback moth-infested artificial diet cakes using a chemical stimulant made from a water extract of collard leaves. Parasitism increased from 19% on artificial diet without the stimulant to 46% on diet treated with collard extract. The wasps were more proficient at stinging larvae, and the sex ratio of wasps produced was more like field populations (about 2:1 male:female) when left confined wit larvae for 48 h.

Last Modified: 11/27/2014
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