Effects of Intraguild Predation of Lysiphlebus Testaceipes by Chrysoperla Rufilabris Larvae

Abstract

Winter wheat (Triticum aestivum L.) is a major commodity grown in the Southern Great Plains. The most common and destructive pest in winter wheat is the greenbug (Schizaphis graminum Rondani). Fortunately, the greenbug has several natural enemies including the endoparasitoid wasp Lysiphlebus testaceipes Cresson and predatory lacewing larvae. These organisms comprise a 'guild' of greenbug natural enemies. When one guild members consumes another guild member it is termed intraguild predation. The studies conducted in this thesis examine how Chrysoperla rufilabris Burmeister biology is affected when involved in intraguild predation interactions with L. testaceipes. Studies involved documenting intraguild predation effects on lacewing larval feeding capability and handling time, as well as larval development, survival and adult body weight. First and third instar C. rufilabris were capable of attacking and consuming mummified greenbugs during 30min feeding observations. Handling times for first instars differed significantly for larvae supplied mummies versus greenbugs; however, there were no differences among the feeding parameters for third instars. Lacewing larvae were reared on 2mg/day diets: unparasitized greenbugs, pea aphids, mummies, and mummies plus a moist cotton ball. Larvae supplied either mummy diet had lower survival for all larval instars and the pupal stage. Development was significantly shorter for larvae supplied the greenbug diet in the first instar and pupal stage. However, there were no differences in total preimaginal survival and development among the diet treatments.