The effectiveness of endemic predators and parasitoids as biological control agents of the greenbug,Schizaphis graminum(Rondani), was experimentally evaluated during 1985 and 1986 in Kansas winter wheat,Triticum aestivum, and grain sorghum,Sorghum bicolor.Mechanical exclusion was used as the experimental method of evaluation. The coccinellidsColeomegilla maculata lengiTimberlake,Hippodamia convergensGuèrin, andScymnusspp. were the predominant predators of greenbugs in sorghum and comprised 89% of the predator population.Lysiphlebus testaceipes(Cresson) was the most abundant primary parasitoid in sorghum. The natural enemy complex was able to suppress experimental greenbug densities at all stages of sorghum growth from 3-leaf through the boot stage. The impact ofL., testaceipeson greenbugs was sporadic between locations. In winter wheat,H. convergenswas the most abundant natural enemy and significantly suppressed greenbug densities. Natural enemies, primarily coccinellids, consistently reduced experimental greenbug populations in winter wheat and grain sorghum.