Bean Leaf Beetle (Coleoptera: Chrysomelidae) Herbivory on Leaf, Stem, and Pod Components of Soybean

Soybeans (Glycine max L. Merrill) in field cages were infested in a normal year (1987) and a drought year (1988) with adult bean leaf beetles, Cerotoma trifurcata (Forster), to ascertain the feeding behavior of this pest during late season (mid-August to mid-September). Pod-surface injury, pod clipping, defoliation, and stem-surface feeding occurred simultaneously. Regression analyses provided equations relating bean leaf beetle feeding days (area under bean leaf beetle density-time curve) to pod, leaf: and stem injury. These analyses indicated that a beetle will feed on an average of 0.494 pod per day in nonnal years and 0.184 pod per day in drought years. Significant differences in pod loss among various levels of beetle infestation were detected only in 1988, with an average of 0.125 pod lost per bean leaf beetle per day. A significant trend in defoliation with increasing bean leaf beetle feeding days occurred in 1987, with an average of 0.384 cm21eaftissue removed per adult per day. Regression analyses also indicated that an average of 0.190 to 0.495 stem lesion was caused per adult per day.