White grub control update

Peak activity periods for adult scarab beetles are now passed, and that means that annual white grub season is upon us. If you are faced with limited conventional options for managing white grubs consider using entomopathogenic nematodes or fungi (EPN, EPF) to keep grubs in check.

All white grub larval stages are susceptible to entomopathogen infection, but susceptibility decreases by as much as 40-60% as grubs mature. As a result, entomopathogen-based products should be applied as soon as possible once white grub eggs hatch and larvae are detected in soil. At present, most annual white grubs, including Japanese beetle, European chafer, and Oriental beetle, are either still in the egg stage or have progressed to first or second instar larvae, so mid-to-late August is the time to apply entomopathogen- based products to areas with known chronic infestations or to get out there and begin scouting for new white grub populations.

Many entomopathogens are available commercially for use as a biocontrol against insect pests, however care should be taken to select the right product for the pest at hand. Products containing the entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae and the nematodes Steinernema feltiae and Heterorhabditis bacteriophora have all been shown to cause mortality in white grubs, but H. bacteriophora in general shows the greatest efficacy. Entomopathogenic nematodes are also the only biological control product not registered by the EPA, and are thus available for use on NY school grounds.

For more information on instructions and considerations for using entomopathogens to control white grubs in turf visit www.biocontrol.entomology.cornell.edu or consult the 2015/16 Cornell—from Dr. Frank Rossi’s blog, shortCUTTS