You Are Here: Management Updates 2008 Archive August 28, 2008

Date: August 28, 2008
Category: Insects
Subject: White Grubs

Here come the grubs!
It is that time of year again. White grubs are starting to show up in turf around the region. So if you have some areas that are looking a little parched, now would be a good time to take a closer look! Soil moisture is likely to be the main driving force in determining where grub activity will be greatest. Adult females look for sites that have just the right amount of soil moisture - if it is too wet, the eggs may not develop and if it is too dry, the tiny grubs may not be able to find healthy roots quickly enough after they emerge.

Areas that received steady rainfall throughout the summer may experience higher grub populations than usual, especially of Japanese beetles and oriental beetles. In areas that received lots of rainfall this year and flooded on at least one occasion during July or August, you might find grub populations showing up in sites that are a little "higher and drier" than usual. In other words, if there were some areas that were submerged more than a few days earlier in the summer, when eggs were just being laid or tiny larvae were just beginning to hatch, those areas may be less likely to experience heavy grub activity.

So get out there now and take a look. If you find grubs that are already well established, you can make a curative application to clean up the populations. Trichlorfon (Dylox™) is always a good quick option - but remember that it cannot be used on school grounds in Massachusetts and there are many other turf areas that are restricted in other states as well.

Dr. Dave Shetlar reports that there are several field reports from trials conducted by turf entomologists around the country that suggest neonicotinoids can be used in late August and still provide curative control, so that may be an option for those who cannot use trichlorfon. However, I am not sure whether any of those trials were conducted on European chafers or oriental beetles, which in general are a little trickier to control than Japanese beetles or masked chafers.

Meanwhile this would also be an excellent time to apply entomopathogenic nematodes (EPNs) if that is the approach you plan to use. See several previous messages for a recap of EPNs on grubs. Briefly, the only nematode that is readily available commercially for homeowners that works on white grubs is Heterorhabditis bacteriophora (HB). We have had some success with this species of nematode against Japanese beetles, oriental beetles, and European chafers. But Albrecht Koppenhofer, perhaps the world's expert on interactions of EPNs and white grubs, reports that HB usually works well on Japanese beetles but is quite inconsistent (and often ineffective) against oriental beetles or European chafers. So let the buyer beware!!!

Submitted by: Dr. Pat Vittum

DISCLAIMER - As always, it is the responsibility of the applicator to verify the registration status of any pesticide BEFORE applying it. Different states have different regulations as well. The author and the University of Massachusetts are not liable for any consequences of any pesticide "recommendations". Mention of any trade name is not to be considered endorsement of a product.

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