You Are Here: Management Updates 2007 Archive May 10, 2007

Date: May 10, 2007
Category: Insects
Subject: White Grubs, May Beetles

It is that time of year again - the grubs are up in the root zone, munching happily.

A few frequently asked questions:

1.  Should we apply products that contain imidacloprid (Merit™, and now that it has gone off patent, several other products as well) now?

Several turf entomologists have tested spring applications of imidacloprid and found that it does not reduce populations of grubs that are present in the spring. So even though some of the products purport "season long control" with imidacloprid, we do not recommend that turf managers use that active ingredient in the spring in New England. (Keep in mind that imidacloprid normally takes a couple weeks to start having a visible impact on grubs.)

In some areas of the country, May applications of Merit™ are appropriate because they can reduce populations of other turf pests, such as billbugs. But in New England, our grub complex is just that, complex. Many turf managers are dealing with European chafers and/or oriental beetles, and imidacloprid applications targeting these species have to be done more "precisely". Aiming to treat when the adults are laying eggs (usually late June or later for European chafers, early July or later for oriental beetles) would be a good plan.

2.  What about the other new products that are related to imidacloprid?

There are two "new" products that are in the same chemical group as imidacloprid. Chlothianidin, sold as Arena™ (through Arysta Life Science), was registered last year, and many people have been using it in New England. I am not aware of any trials that have determined whether spring applications of Arena™ will work on spring grubs. But we did conduct a trial last fall that indicated that chlothianidin can work more quickly than imidacloprid.

The other new product is thiamethoxam, sold as Meridian™ (through Syngenta). It received federal registration in early 2007, and several of the New England states have also registered it. Again I am not aware of any field trials that have been conducted to determine whether spring applications of Meridian™ will reduce spring grub populations.

Both companies claim that their product (chlothianidin or thiamethoxam) is active against a wider range of turf insects than is imidacloprid.

3.  So what should I do if I have major grub problems right now?

There are only two insecticides available that work quickly enough to reduce spring grub populations. Those are Dylox™ (trichlorfon) and Sevin™ (carbaryl), both quite fast acting and soluble. Neither of those products can be used on school grounds in Massachusetts (and Dylox™ cannot be used on any turf in Maine).

Grub feeding should begin to decline relatively soon (within the next three or four weeks) so in most cases, it might be best to just manage the damage for the next few weeks. Monitor where the grub activity is now, and figure that in many situations, those areas will be subject to attack again later in the summer when the new adults emerge. Because soil temperatures just began to warm up, the window for spring treatments was shorter than usual this year.

4.  What's new with May beetles?

May beetles are beginning to emerge. I encountered a couple specimens (may they rest in peace) last night in my own back yard. There are many species in the Phyllophaga genus, some of which have annual life cycles like our more common Japanese beetles and oriental beetles. But most Phyllophaga species in New England take two or three years to complete a life cycle. The adults lay eggs from late May through mid July, depending on the species and the location.

For now, watch with curiosity. In most situations the Phyllophaga populations are sporadic and not normally very dense. If a heavy population does develop, you can expect major disruption from skunks, raccoons, or other foragers. The fun will begin in August as the grubs grow larger.

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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