You Are Here: Management Updates 2002 Archive October 2, 2002

Date: October 2, 2002
Category: Insects
Subject: White Grub Control

As usual, white grubs are rearing their ugly heads this autumn. The dry conditions earlier in the summer resulted in delayed oviposition, especially for Japanese beetles, but now the grubs are approaching their third instar (largest stage) and appear to be quite healthy.

In many cases grub damage is just becoming apparent, especially where skunks or raccoons are rummaging. We are RUNNING OUT OF TIME to manage grub populations this fall. The only chemical option that would provide any relief at this point is trichlorfon (DYLOX). This product, available
in granular or sprayable formulations, is very fast-acting (it takes two or three days until you begin to see dead or dying grubs), but breaks down very quickly. It is quite soluble in water, so should not be used near surface water.

Meanwhile, as I interpret the Massachusetts "Act Protecting Children and Families from Harmful Pesticides", DYLOX cannot be used on outdoor grounds of any school, day care
center, or school age childcare program because the USEPA has classified trichlorfon as a likely carcinogen (at high doses). So people managing athletic fields at educational institutions are certainly between a rock and a hard place. Your only option may be to roll the fields regularly (to try and improve rooting) or to close the fields (to avoid lawsuits pertaining to bad footing).

For those who do have access to DYLOX, remember that we are already past the period we normally recommend its use (mid September), but because this fall has been so mild, soil temperatures probably are still high enough right now (1 October). There are no field studies to confirm, but we suspect that soil temperatures should be at least 60 F when DYLOX is used.

Also remember that the application MUST BE WATERED IN, with at least 0.25 inch of rain or irrigation. And finally, remember that the active ingredient is sensitive to high pH, so if the water source is alkaline, consider dropping the pH with an additive of some sort.

There is one entomopathogenic nematode that has looked promising in our trials over the years, Heterorhabditis bacteriophora. These nematodes are available in small quantities, but tend to be hard to find. Again soil temperatures need to be above 60 F, and applications must be watered in
IMMEDIATELY to help the nematodes move down to the soil. My best guess is that nematode applications would have to be in place by the end of this week (4 October) to have any real chance of success this year, and even then they may only provide 70 to 75% control.

You must read the small print regarding nematodes. There are several other species "out there". Steinernema carpocapsae is perhaps the easiest one to obtain, but trials conducted throughout the Northeast (including Cornell, Penn State, and Massachusetts, among others) have shown S. carpocapsae to be very inconsistent or downright ineffective against white grubs. So save it for other insect pests, so you won't be disappointed if it doesn't work on grubs.

Finally, this would be a good time to MONITOR grub activity. Sketch maps that note the areas where you are seeing damage now. Include actual grub counts if at all possible. You may be able to provide some relief in those areas next spring, and certainly you may want to concentrate your grub management efforts in those same areas next year.

Remember that we are still more than willing to identify grubs to species for you. We just ask that you send us 75 to 100 grubs from a given location. CALL FIRST to get instructions on how to package the grubs - we don't want the post office folks mad at us!

- Submitted by: Dr. Pat Vittum