Author
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Hu, Jing - Hu |
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Gelman, Dale |
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Blackburn, Michael - Mike |
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Submitted to: Archives of Insect Biochemistry and Physiology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 10/8/2001 Publication Date: N/A Citation: N/A Interpretive Summary: Whiteflies attack more than 500 species of food, fiber and ornamental plants causing crop losses that total hundreds of millions of dollars. Concern about the development of pesticide resistance in whiteflies as well as the need to reduce pesticide usage because of environmental considerations has resulted in increased emphasis on the use of cost-effective biological control strategies in IPM programs. These includ the enhanced use of natural enemies such as the parasitic wasp, Encarsia formosa, which has been found to successfully control the greenhouse whitefly in greenhouses. Because E. formosa is such a good biological control agent, there has been considerable interest in artificially rearing this wasp. However, little information is available concerning the regulation of its development including the host-parasite interactions required for E. formosa to complete its life cycle. In this work, we present results concerning the developmental rate, emergence rate, emergence pattern and adult longevity of this useful biological control agent. We report that the environment provided by the whitefly 3rd or early 4th stage is the best for promoting synchronous development of high quality wasp parasites. Previous reports concerning a trigger necessary for the wasp to complete development were shown to be incorrect. Rather, the parasite's next to the last molt appears to require conditions that are associated with the initiation of adult development in the host whitefly. Information will be useful to entomologists for the development of short and long term artificial rearing systems for this useful parasitic wasp. Technical Abstract: Encarsia formosa, a tiny parasitoid wasp has been used successfully to control greenhouse whiteflies (GHWFs) in greenhouses in many countries throughout the world. Therefore, there has been considerable interest in developing methods for artificially rearing this wasp. However, little information is available concerning the regulation of its development including the host-parasitoid interactions that are required for the parasitoid to complete its life cycle. Here we report that parasitoid developmental rates differed significantly based upon the host instar parasitized. Development was faster when 3rd and 4th instar GHWFs were offered for parasitization than when 1st or 2nd instars were used. Although emergence rate did not differ in regard to host instar parasitized, adult longevity as well as adult emergence pattern varied greatly depending upon the instar parasitized. When 3rd and 4th instar GHWFs were selected for oviposition, adult wasps lived significantly longe than when 1st or 2nd instars were used; also, there was a sharp emergence peak on the 2nd day after emergence was first observed (reduced or absent when 1st or 2nd instar GHWFs were parasitized) and the emergence period was reduced from between 8 and 11 days to 5 days. In general, the younger the instar parasitized, the less synchronous was parasitoid development, but, previous reports that E. formosa will not molt to the 2nd instar until the host has reached its 4th instar were not confirmed. Our results indicate, however that a condition(s) associated with host pharate adult formation is required for the parasitoid's final larval molt. Results reported here should facilitate the development of short and long term in vitro rearing systems for E. formosa. |
