Parasitoids of the bean leaf beetle (Coleoptera: Chrysomelidae) found in Nebraska soybean fields

The bean leaf beetle, Cerotoma trifurcata (Forster) (Coleoptera: Chrysomelidae), is the major insect pest of soybean in Nebraska and throughout much of the midwestern United States. Natural enemies of the bean leaf beetle have been reported in other states, but none have been reported in Nebraska. In this study, bean leaf beetle adults were obtained by aspirating those found on soybean plants early in the season and by sweep net once plants were in the V4 stage (approximately 0.33 meter tall). Sampling was done in 1997 and 1998 in soybean fields at the University of Nebraska Agricultural Research and Development Center in Saunders County in east-central Nebraska. Beetles were taken to the laboratory and reared to monitor for parasitoid emergence or preserved in ethyl alcohol for later examination for external parasitic mites. Nine tachinid parasitoids emerged from nine of the beetles that were collected in 1997 and identified as Celatoria sp. (species undescribed) (Diptera: Tachinidae). Percentage of beetles infested with the parasitoid ranged from zero to 1.1. Ectoparasitic mites, identified as Trombidium hyperi Vercammen-Grandjean, Van Driesche, and Gyrisco (Acari: Trombidiidae), were found under the elytra on six of the preserved beetles from 1997 and 16 of the beetles from 1998. A total of 8 mites were found in 1997 and 55 were found in 1998. Percentage of beetles infested with the mites ranged from 0-4 in 1997 and from 0-40 in 1998. This is the first report of natural enemies of the bean leaf beetle from Nebraska. This information may be useful to those developing integrated pest management strategies for the bean leaf beetle in the future.