Degree-Day Requirements for Development of the Bean Leaf Beetle (Coleoptera: Chrysomelidae) Under Two Rearing Regimes

Bean leaf beetles, Cerotoma trifurcata (Forster), were reared from egg to adult at temperatures from 18 to 32°C. To maximize larval survivorship, larvae were fed cotyledons of cowpea, Vigna unguiculata (L.). To test the effect of larval diet, other larvae were fed nodulated roots of potted soybean plants, Glycine max (L.) Merrill. When larvae fed on cotyledons, C. trifurcata required 491 ± 8.1 DD (>11.58°C) to complete development from egg to adult. The relationship between developmental rate and temperature was significantly different when larvae fed on soybean roots, where C. trifurcata required 646 ± 17.4 DD (>7.61°C) to complete development. Degree-day requirements under each rearing regime were not significantly different from requirements of field populations, as estimated from 7 yr of field data (9 C. trifurcate populations total). To complete development, F)-generation field populations required 495 ± 19.6 DD (>11.58°C) or 674 ± 28.7 DD (> 7.61°C). F2- generation field populations required 542 ± 42.5 DD (> 11.58°C) or 740 ± 58.2 DD) (>7.61°C).