Influence of Patch Plant Density on Herbivory Levels by Etiella zinckenella (Lepidoptera: Pyralidae) on Glycine max and Crotalaria pallida

Abstract

Experiments were conducted to determine the influence of the density and size of patches of soybeans ( Glycine max (L.)) on the extent of pod damage by the lima bean pod-borer Etiella zinckenella (Treitschke). In addition, an evaluation was made of changes in rates of parasitism as a function of changes in patch characteristics. Low-density plots had a greater proportion of pod damage than did high-density plots. Plot size did not influence the proportion of pods attacked per plant. Larval parasitoids of E. zinckenella , in general, were not influenced by plant density but were influenced by host herbivore density. Other experiments were conducted to determine if mixtures of soybeans with a feral host, Crotalaria pallida Ait, a species in the Fabaceae, would influence damage by the pod borer or parasitism. No differences were observed between mixed species plots and pure C. pallida or pure soybean plots, in the number of E. zinckenella larvae per plant raceme nor in the level of parasitism. The abundance of pods produced by plants as a function of cultivar type, patch characteristics and time of season were also recorded.