You Are Here: Management Updates 2009 Archive July 8, 2009

Date: July 8, 2009
Category: Insects
Subject: White Grubs

Several people have asked me recently what the options are for controlling white grubs. The questions center around the rain we have had throughout June, and the degree of soil saturation in many parts of the Northeast. Any grub insecticide should be watered in as soon after application as possible and right now, most of you don't want to irrigate!!!

This update will center only on the preventive options that are available to control white grubs. The preventive options include several neonicotinoids and a new product, Acelepryn™, in a different chemical class.

There are three neonicotinoids available to commercial applicators: chlothianidin (Arena™), imidacloprid (Merit™), and thiamethoxam (Meridian™). Merit™ went off patent a few years ago and there are several generic products available now that contain imidacloprid. In addition there are some homeowner formulations that contain imidacloprid, including Bayer's "Advanced Season Long Control™l". The neonicotinoids are effective against European chafers, Japanese beetles, and oriental beetles, but not against asiatic garden beetles.

In addition there are three products that combine a neonicotinoid with a pyrethroid. The neonicotinoid part of the combination is effective against white grubs (except asiatic garden beetles), while the pyrethroid part of the combination is effective against many of the surface and thatch insects, such as billbugs, chinchbugs, and caterpillars. The products in this group include: Allectus™ (Merit™ plus Talstar™), Aloft™ (Arena™ plus a generic form of bifenthrin), and Maxide™ (Meridian™ plus Scimitar™). Allectus™ and Aloft™ are available for commercial use only right now, while Maxide™ is being marketed for homeowners through some of the "big box" stores.

The ideal time of application of a neonicotinoid to control white grubs is while the adults are laying eggs. Most years in New England that would be between mid June (in areas with heavy European chafer activity) and mid August (more northern locations that have primarily Japanese beetle populations). This year the Japanese beetle activity appears to be a little delayed, probably because of the wet soils we had through most of June, so applications probably can be delayed a little bit in many locations.

As a general guide, I would suggest that neonicotinoid applications should be made by the middle to end of July in eastern Massachusetts, especially if the population is known to be primarily European chafer. Applications can be made into mid August in areas that have more Japanese beetles or oriental beetles.

We conducted one small field trial last September, and some of my colleagues report similar results. We found that late season applications (treatments on 17 September) of Aloft™, Dylox™, or Merit™ reduced grub populations but we did not see the reduction until four weeks after the application. At that time, Aloft™ was significantly more effective than Merit™ (96% control vs 54% control), with Dylox™ in the middle at 77% control. Only Dylox™ reduced the grub count significantly nine days after application. My take on these numbers - if you have a grub problem that needs immediate attention in September, Dylox™ is still your best bet but Aloft™ might provide some relief if Dylox™ is not available to you.

The newest insecticide on the market for preventive grub control is chlorantraniliprole (Acelepryn™). This is in a new class of chemistry and has a very low level of toxicity to vertebrates (and to bees, wasps, and ants). It is most effective against white grubs if it is applied between mid April and early June.

So right now you should have some options. If we catch a break in the weather and soils dry out a little, you should be able to get some of those preventive products out soon!

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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