Survivorship of Experimental Green Cloverworm (Lepidoptera: Noctuidae) Pupal Cohorts in Soybeans1

Abstract

The survivorship of pupal green cloverworms (GCW), Plathypena scabra (F.), was studied experimentally in Iowa soybean fields during 1978 to 1980. During 1978 and 1980, predation was the primary pupal mortality factor, accounting for 37.8 and 60.0% mortality, respectively. Two categories of predation were identified: “eaten” and “missing” pupae. More pupae were “missing” and fewer pupae were “eaten” in field plots 0 to 4 m from the fencerow than in plots 30 to 34 m or 76 to 80 m from the fencerow. During 1979, a single severe thunderstorm destroyed 82.8% of the cohorts. Laboratory feeding trials identified 10 species of crickets, ground beetles, and rodents as GCW pupal predators. Exclusion cage experiments during 1980 showed that the northern field cricket, Gryllus pennsylvanicus Burmeister, accounted for 60 to 87% of total pupal predation. The combined impact of this cricket and several ground-foraging birds seemed to account for the high levels of pupal predation observed adjacent to the fencerow.