You Are Here: Management Updates 2007 Archive April 27, 2007

Date: April 27, 2007
Category: Insects
Subject: Annual Bluegrass (Hyperodes) Weevil

Annual bluegrass weevils are definitely moving. The warm weather last week-end seems to have spurred the adults into moving away from their overwintering sites and toward the fairways and other short cuts of turf. Since late March, we have been collecting samples every other week from four golf courses between Hartford and Westchester County, NY, and the samples taken early this week were the first to indicate that weevils were nearing the fairways. This movement is about a week, or perhaps two weeks, later than "normal", primarily because of the cool weather that dominated the region in early and mid April.

 "When should I treat?"
Several people have e-mailed or called in the past week to ask when they should be making their spring application that targets adults. The answer depends on your local conditions. As always, it is best to wait until Forsythia have passed the "full bloom" stage and moved on to where the new leaves are also evident. (I call this the "half green - half gold" stage, because both colors are very visible.) For those of you in the metropolitan New York area, that is probably now! For those of you around Hartford, some areas of the golf course may be at that point, while others are not yet. And those of you in western Massachusetts and points north probably need to wait a little longer.

 "What should I use?"
As most golf course superintendents in the Northeast are aware, Dr. Rich Cowles (Connecticut Agricultural Experiment Station, Windsor, CT) began investigating the possibility that ABWs were developing resistance to pyrethroids a couple years ago. Some of the data that he has been sharing at regional conferences certainly indicates that some weevil populations are not as susceptible to pyrethroids as other populations. In general, the sites where he has found what might be described as resistance have been locations with multiple generations of weevils each year and a history of several applications of one or another of the pyrethroids each year for several years.

We do not yet know how widespread this phenomenon is, but whether or not a given weevil population has developed resistance to pyrethroids, it would be a good idea to begin to reduce our reliance on the pyrethroids. (Keep in mind that pyrethroids are also often used in the summer to control black cutworms and other caterpillars.) But that is easier said than done with annual bluegrass weevils, because we have limited options against the adults.

Right now there are only two kinds of insecticides that should be used to target ABW adults - the pyrethroids or chlorpyrifos (Dursban™). These materials are very insoluble, and tend to be bound up in the organic matter of the thatch, making them ideal for targeting adults.

I have been hearing rumors that some superintendents or distributors are considering using indoxacarb (Provaunt™) to control ABW adults. Please note that there is little or no data to support that use. The product has looked encouraging when used later in the year (as a curative targeting larvae). DuPont, the registrant of Provaunt™, arranged for field trials in 2006 to determine whether Provaunt™could be used as a preventive (targeting adults) but all three test sites were literally washed out by the heavy rains last spring. The company is trying again this year (and has arranged for even more test sites), and will have considerable information by the end of June, once those field trials have been evaluated. But for now, you might consider delaying any Provaunt™ applications until right after the larvae have hatched out and begun feeding.

Also remember that several years of field trials have indicated that imidacloprid (Merit™) by itself is very inconsistent against annual bluegrass weevils. Sometimes it seems to reduce the population and sometimes it does not. There is limited data available regarding how effective the other neonicotinoids might be against ABW, including chlothianidin (Arena™) and thiamethoxam (Meridian™). Again we should know a lot more by late June, since several field researchers have been asked to include those two compounds in ABW field tests this year.

A partial list of pyrethroids and the most common trade names for those compounds includes:

• bifenthrin (Talstar™)
• cyfluthrin (Tempo™)
• lambda-cyhalothrin (Battle™, Scimitar™)
• deltamethrin (Deltagard™)

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.

Links followed by the symbol are external links that open in a new window.