You Are Here: Management Updates 2005 Archive August 15, 2005

Date: August 15, 2005
Category: Insects
Subject: Annual Bluegrass (Hyperodes) Weevil

This is a recording - 2005 has proven to be the most challenging I have ever seen for managing annual bluegrass weevils (Hyperodes weevils). Most years the first generation causes the most problems and then numbers tail off through the remainder of the summer. So damage is usually most severe in June, and then other things (like diseases!) take precedence.

But this year populations have just kept on building through the summer. I have had reports of severe damage from several superintendents. We have been tracking populations on a golf course in Westchester County and there have been three generations already at that site!

The good news is that for those of you currently seeing adults moving on the surface, the worst should be over. Some of the adults that we see now will produce yet another round of eggs, but it will take at least three weeks for those eggs to mature to large larvae that are capable of damaging the turf. And surely we will have gotten a break in the weather by then. (Frankly, as an aside, if we are still locked in heat and humidity three weeks from now, there will be little turf left anyway as a result of the environmental stresses and the high temperature diseases running rampant.)

So to get back to the Hyperodes saga - for those of you south of Hartford, CT, the worst really should be over now. There may still be a few larvae feeding here and there, but the next "flush" of larvae should not appear until later in the month when other stresses are beginning to ease. For those of you in northern Connecticut (north of Hartford) and much of Massachusetts, you may be in the middle of the worst right now, but weevil pressure should be easing within a few days. Again if you see large numbers of larvae feeding actively, you may get some relief by hitting those areas with trichlorfon (Dylox™). Take all the usual precautions to guard against phytotoxicity.

Finally, the rumors are flying regarding whether the weevils have developed resistance to any of the pyrethroids. As you know, many superintendents have been using pyrethroids for several years now (things like Tempo™, Talstar™, Battle™, Scimitar™, Deltagard™, and others) and other species of insects have shown the capability to develop resistance to pyrethroids in other crops. Up until this year, we had had no evidence that annual bluegrass weevils had developed resistance.

Based on recent conversations, it is my understanding that Dr. Rich Cowles (UConn, Windsor Agricultural Experiment Station) has collected adult weevils from two golf coursese near Hartford. He screened the weevils from one of those golf courses and, according to my sources, reported that there was evidence of resistance in those weevils. I believe he has not yet tested the weevils from the other golf course. I have been unable to confirm any of this with Dr. Cowles directly but hope to contact him soon.

But if it turns out that these weevils have indeed developed resistance to pyrethroids, it would explain some of what we have been experiencing this year. It is too early to jump to conclusions, and way too early to panic. There is no evidence that all weevil populations have developed resistance. In fact, resistance often is "spotty", showing up in some places but not in others. Meanwhile, there are non-pyrethroid alternatives that should continue to work in 2006 and years to come. We may just have to adapt a little bit and change the timing of applications, depending on the materials we are using and the stages of the insect we need to target.

So as always, hang in there and keep monitoring the &$^%%*#s. Cooler temperatures will eventually prevail, and we can breathe again.

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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