Ground Covers Influence the Abundance and Behavior of Japanese Beetles

Ground covers were tested for 3 consecutive yr for their effect on Japanese beetle, Popillia japonica Newman (Coleoptera: Scarabaeidae), abundance and behavior in a blueberry planting. Alsike clover (Trifolium hybridum L.), buckwheat (Fagopyrum esculentum Moench), perennial ryegrass (Lolium perenne L.), and bare ground were compared within row-middles for their effect on abundance of adult female beetles, female beetle behavior after landing, density of larvae in the soil, and survival of larvae. Adult beetles were consistently most abundant on buckwheat, followed by clover and ryegrass, while they were generally absent from bare ground plots. Larval density was three times greater in ryegrass and clover than in buckwheat, with the fewest found in bare ground. There was high variability in larval survival within treatments, but overall survival was highest in plots with ryegrass. Observations of adult beetles revealed that the proportion of time spent feeding and the frequency of feeding were higher on buckwheat and clover than on ryegrass, and the average duration of digging bouts lasted longer on ryegrass than on the other two plant treatments. These results reveal that adult P. japonica behavior is affected by cover crops and that this behavior translates into variation in larval density of this pest.