Impact of halofenozide, imidacloprid, and bendiocarb on beneficial invertebrates and predatory activity in turfgrass

Imidacloprid, a chloronicotinyl, and halofenozide, a bisacylhydrazine ecdysteroid agonist, recently have become widely used for residual control of scarabaeid grubs in turf. We evaluated their impact on earthworms and beneficial arthropods in field trials, and tested whether application in late spring might interfere with subsequent predation on black cutworm, Agrotis ipsilon (Hufnagel), and Japanese beetle, Popillia japonica Newman, life stages in Kentucky bluegrass, Poa pratensis L., turf. Bendiocarb, a short-residual carbamate, was included for comparison. Imidacloprid caused some short-term suppression of earthworms, whereas bendiocarb had severe impact on earthworms, mesostigmatid mites, and Collembola. Pitfall trap captures of predatory coleopteran larvae and hister beetles were reduced by imidacloprid and bendiocarb, but abundance of ants, carabids, spiders, and staphylinids was largely unaffected. Halofenozide caused no reduction in abundance of any group of beneficial invertebrates. Scavenging on fresh-frozen A. ipsilon larvae was reduced for approximately 1 wk after use of imidacloprid or bendiocarb, but predation rates on eggs or pupae of A. ipsilon, and on implanted P. japonica eggs, were unaffected. This work suggests that application of halofenozide or imidacloprid, followed by irrigation, will have relatively little impact on beneficial invertebrates, although both compounds are persistent enough to control P. japonica and Cyclocephala spp. grubs eclosing several months later.