PERSISTENCE OF CONTROL OF JAPANESE-BEETLE (COLEOPTERA, SCARABAEIDAE) LARVAE WITH STEINERNEMATID AND HETERORHABDITID NEMATODES

Field tests were conducted in 1986 and 1987 to evaluate control of Japanese beetle larvae, Popillia japonica Newman, in turfgrass plots by heterorhabditid and steinernematid nematodes. Heterorhabditis bacteriophora Poinar (NC strain) reduced populations a maximum of 60%, 34 d after a fall 1986 treatment Control increased to 96% before pupation the following spring, and was 93-99% of the next larval generation. Application of Steinernema (= Neoaplectana) carpocapsae Weiser (All strain) provided a maximum of 51% control after 34 d, 90% the next spring (290 d after treatment), and 0% after 386 d. A spring 1987 application of H. bacteriophora resulted in 68% control 28 d after treatment, and up to 67% of the following generation of Japanese beetle larvae in the fall (138 d after treatment). H. bacteriophora (HP88 strain) gave 100% control after 28 d in the spring of 1987, and 93-97% control of the next generation of larvae. No adverse effects on nontarget organisms (mites or collembola) were observed 28 d after treatments with any of the nematodes. Our data show that nematodes reproduce in Japanese beetle larvae, survive in the field in turfgrass, and have an influence on target hosts for a longer period of time than previously demonstrated.