You Are Here: Management Updates 2009 Archive March 16, 2009

Date: March 16, 2009
Category: Insects
Subject: White Grubs

The warm temperatures of this past week have gotten people to thinking that perhaps spring is just around the corner. If that is true, then it must be time to start thinking about turf insect activity.

White grubs have been deep in the soil profile for the winter but now that the air temperatures are rising, the frost line is rising as well, and the grubs will not be far behind. That means there will be many people wondering about the best approach for grub control this year. (In fact many of you in southeastern Massachusetts may already be seeing new grub damage, courtesy of the European chafer.)

One of the traditional approaches has been to apply a neonicotinoid (something like imidacloprid, or Merit™; thiamethoxam, or Meridian™; or chlothianidin, or Arena™). The labels for all these products suggest that the ideal timing of application is when the adults are laying eggs (anywhere from mid June to late July, depending on your location and the species of grub). You can probably push that a little bit earlier and still get good control. But there are no formal field trials that have been conducted that can tell us whether spring (i.e., April or May applications) will control grubs that are present in the spring.

Keep in mind that the combination products (Allectus™ contains Merit™ plus Talstar™, Aloft™ contains Arena™ plus a generic form of bifenthrin should be used in the same way if targeting white grubs. Applying when adults are laying eggs would maximize their effectiveness against grubs. But of course you might also be trying to get the benefit of the pyrethroid, so a slightly earlier application is tempting.

The best curative option to manage grubs that appear in the spring remains trichlorfon (Dylox™). This is a very soluble product and moves readily through the thatch. If you need to clean up a grub problem, apply Dylox™ as soon as the soil temperatures warm up to at least 55 to 60 degrees. Remember that Dylox™ is on the "do not use" list for Massachusetts school grounds.

There is another approach that will be an option for most of you this year. Acelepryn™ (chlorantraniliprole) is a new insecticide from DuPont, which received federal registration in April 2008. At the time of writing (16 March), only two states have not yet approved it: New York and Hawaii. That means it is available in all the other states. I believe it will eventually be available in a flowable (soluble concentrate) formulation and a granular formulation.

Acelepryn™ has activity against many different turf pests and is extremely effective against white grubs. It looks very promising against annual bluegrass weevils (ABW) in many situations, and also works against billbugs and caterpillars. In fact at the ABW rate, it provides 10 to 12 weeks of caterpillar control.

Acelepryn™ has a totally new mode of action (it has to do with movement of calcium ions in muscle cells). The receptor site on insects is highly sensitive, while humans and other vertebrates are virtually insensitive to the action. As a result, USEPA did not require that DuPont include a signal word on the product - not even Caution.

Acelepryn™ will be most effective if applied between 15 April and 1 June. In fact DuPont is guaranteeing applications made between those dates! The rate of application can vary between 8 and 16 fluid ounces per acre. The product issystemic and takes a while to get into the plant tissue. The low rate, applied in April or May, will have enough residual to control white grubs in the fall (but will not control grubs that are present in the spring). The higher rate normally would be used in some of the "tough to manage" ABW populations or for slightly later summer applications targeting grubs.

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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