The turf habitat is surprisingly rich in natural enemies of turf pests. In this Kentucky
study, ants were by far the most abundant predators, accounting for more than half the predators
found, followed by spiders, rove beetles, ground beetles, tiger and hister beetles. These predators can
have a significant impact on turfgrass pests. Up to 74% of Japanese beetle eggs, and 53% of fall
armyworm pupae placed in pesticide free plots of Kentucky bluegrass were removed by natural
enemies in 48 hours. Soil applications of carbaryl, cyfluthrin, and isazofos in 10 m X 10 m plots
greatly reduced the populations of most of these natural enemies for 6 to 10 weeks. Ant
populations were suppressed even longer. Use of soil insecticides in early summer for billbugs,
chinch bugs, or sod webworms has the potential to increase problems with white grubs by killing
predators' eggs and young larvae. When the three soil insecticides were applied in mid-June,
predation on Japanese beetle eggs placed in soil was reduced by more than half in the isazofos
and carbaryl plots. By the end of the season, naturally occurring Japanese beetle grub densities
was highest in isazofos treated plots. Turf managers seeking to conserve natural enemies of white
grubs should use selective pesticides such as Bacillus thuringiensis when possible for sod
webworm, and restrict pesticide applications for early season pests to areas where problems
occur. Applications of soil insecticides for areas affected by white grubs should not be applied
before eggs hatch. This can minimize the impact of the pesticide application on natural enemies
by giving them a chance to feed on grubs, and providing them with safe havens in the turf.
Source: Terry, L.A., D.A. Potter, and P.G. Spicer. 1993. Insecticides affect predatory arthropods and predation on
Japanese beetle (Coleoptera: Scarabaeidae) eggs and fall armyworm (Lepidoptera: Noctuidae) pupae in turfgrass.
J. Econ. Entomol. 86:871-878.
