Seasonal Parasitism and Predation of Eggs of the Tobacco Hornworm 1 on Various Host Plants in Kentucky 2

Abstract

Parasitism and predation of eggs of Manduca sexta (L.) (Lepidoptera:Sphingidae) on tobacco; jimson weed, Datura stramonium L.; tomato; and potato were investigated in central Kentucky throughout the season in 1970 and 1971. Heavy parasitism of eggs was found on jimson weed, tomato, and potato. In both years, parasitism of the eggs was greater on jimson weed than on tomato, but the seasonal peak on both plants occurred between mid-August and early September. Parasitism of eggs on potato was less than on jimson weed and tomato, and no egg parasitism occurred on any of the varieties of tobacco: ‘By 21,’ ‘Low alkaloid By 21,’ ‘Ky 12’ and ‘Ky 170.’ However, parasitized eggs were found on one foreign tobacco variety, ‘TI-1298,’ being grown for other tests. The eggs were parasitized by two hymenopterous species: Telenomus sphingis (Ashmead) and Trichogramma minutum Riley; T. sphingis was the predominant species. Parasitism by T. minutum was greater in eggs on tomato than on jimson weed. Predation of M. sexta eggs was low, and the extent of predation varied with the host plants but increased in late-season on all hosts. The stilt bug, Jalysus spinosus (Say), was the major predator.