INSECTICIDES AFFECT PREDATORY ARTHROPODS AND PREDATION ON JAPANESE-BEETLE (COLEOPTERA, SCARABAEIDAE) EGGS AND FALL ARMYWORM (LEPIDOPTERA, NOCTUIDAE) PUPAE IN TURFGRASS

The relative short-term effect of three insecticides on predatory arthropods and their potential to interfere with natural predation on pest insects or to induce resurgences of white grubs were evaluated in Kentucky bluegrass, Poa pratensis L., turf. A single surface application of isazofos in mid-june caused significant short-term reductions in abundance of spiders, ants, staphylinids, carabid larvae, histerids, and other predominantly predatory groups. Carbaryl and cyfluthrin also affected some groups of predators, but their impact was generally less severe than for isazofos. Pupae of fall armyworm, Spodoptera frugiperda (J. E. Smith), and eggs of Japanese beetle, Popillia japonica Newman, implanted into treated or control plots 1-2 wk after treatment sustained predation losses as high as 60 and 74%, respectively, within 48 h. Predation on pupae was not significantly affected by the insecticides, but predation on Japanese beetle eggs was reduced by as much as 70% in plots that had been previously treated with isazofos or carbaryl. Predatory Coleoptera, including Carabidae, Staphylinidae, Cicindelidae, and Histeridae, collected from turfgrass readily consumed Japanese beetle eggs or first-instars in laboratory trials. Plots treated with isazofos during the Japanese beetle oviposition period incurred significantly higher natural populations of white grubs than did control plots. These findings suggest that by disrupting predation on eggs and young larvae, insecticides applied to turfgrass before scarabaeid eggs have hatched could predispose lawns or golf courses to higher densities of white grubs and possibly other pests.