Potential for behavioral and cultural manipulation of Japanese beetle (Popillia japonica Newman, Coleoptera: Scarabaeidae) population

The Japanese beetle, Popillia japonica Newman (Coleoptera: Scarabaeidae), is an invasive insect with potential for range expansion into many of the major agricultural production regions of the world. Popillia japonica is currently the most important insect pest for producers of highbush blueberry, Vaccinium corymbosum L., in the Midwestern United States. At fifteen commercial highbush blueberry farms in Michigan, fields with tilled row-middles had 72% fewer P. japonica larvae than fields with grassy row-middles. Popillia japonica larval populations were similar in the perimeters of tilled and untilled fields. Adult beetles on bushes were significantly less abundant in tilled fields compared to fields with grassy row-middles. The abundance of larvae inside fields during the spring was significantly correlated with early, but not late summer abundance of adult beetles on bushes. Grassy plots between rows of blueberry bushes tilled in spring and kept bare all year had fewer P. japonica larvae than plots retaining perennial ryegrass. Tillage in the spring and in the autumn caused 51% reduction in 2002 and 69% in 2003. Over three years, significantly fewer adult Japanese beetles were found on clover, ryegrass or bare ground than on buckwheat, whereas larval density from natural infestation in these plots in the fall was significantly lower under buckwheat and bare ground than under ryegrass and clover. Significantly fewer eggs that were artificially placed into the soil in these plots developed into larvae under clover and bare ground, than under ryegrass and buckwheat. Female P. japonica observed in the field spend more time digging on ryegrass than buckwheat or clover. These field results indicate differential acceptance of females when choosing an oviposition site. In laboratory behavioral bioassays, females laid more eggs in soil with artificial grass stems compared to bare ground, and preferred for higher stem density and diameter, but did not respond to different stem colors. These findings suggest the possibility for reducing P. japonica populations by changing the vegetation characteristics of blueberry fields. In a survey, Michigan blueberry growers were asked to rate the extent to which P. japonica is a pest within this crop, and to reveal their responses to this pest management challenge. This insect was of concern to the majority of growers that returned the survey (84%), causing additional costs per acre of $72. Increased insecticide use was the major cause of the economic loss. Insecticides and clean cultivation were the main method for controlling Japanese beetle. Japanese beetle has driven changes in row-middle management, indicated by growers who have switched to clean cultivation recently. Many growers were willing to try new cover crops, if they are shown to be effective against Japanese beetle.