You Are Here: Management Updates 2007 Archive June 8, 2007

Date: June 8, 2007
Category: Insects
Subject: Annual Bluegrass (Hyperodes) Weevil

Well, the action has picked up considerably in just the past week! We are hearing of significant annual bluegrass weevil populations - and damage - on golf courses in southeastern Pennsylvania and southern New Jersey. In those areas, the worst should be over for now, as most individuals should have completed the larval stages and are now pupating.

In Westchester County, New York, samples collected on Monday (4 June) were 75% large larvae, less than 5% pupae, and the rest were small or medium larvae. Samples pulled just south of Hartford on Wednesday (6 June) were 20% small larvae, 40% medium larvae, and 40% large larvae.

Paul Heller (turf entomologist at Penn State) and I have seen the same phenomenon in several locations this year. Regular sampling in early spring did not uncover many adults, and we wondered whether the populations would be a little lower than "normal" this year. Even as recently as a week ago, sampling in some sites indicated that most populations were still small larvae, and yet when we collected samples this week, all of a sudden the populations had progressed to large larvae. Neither of us can remember such rapid "explosions" of activity in the past 10 to 15 years. And populations are higher in most locations than we have seen in several years. Each of us has visited at least one site where there are more than 220 larvae per square foot in untreated plots.

Meanwhile annual bluegrass populations seem to be higher than "normal" in several locations, as well. At least there are more seedheads...

For golf course superintendents who are wrestling with ABW damage, here is a quick reminder of your options. The first step is to collect several samples from the areas where the weevils are active, and determine whether most of the insects are larva (they look like grains of rice with brown heads, pupa (cream-colored and kind of diamond-shaped), or adults.

If the insects are mostly larvae, you can get relief by applying trichlorfon (Dylox™). (We have also had good success several years with spinosad, Conserve™, but those trials have been directed against small and medium larvae in the spring, so we don't really know whether Conserve™ can be effective against full-grown larvae.) Dylox™ should provide about 50 to 75% control of the larvae that are present when you treat. Check the label, because while ABW larvae were added to the Dylox™ label a couple years ago, there may be a couple formulations that do not include ABW.

If the insects are mostly adults™, you should consider using one of the pyrethroids. Bifenthrin (Talstar™), cyfluthrin (Tempo™), lambda-cyhalothrin (Battle™, Scimitar™), and deltamethrin (DeltaGard™) are among the more commonly used materials. Note that there are several additional products with the same active ingredient but different trade names. For those of you who are concerned about the possibility of the development of resistance, you can also get good control of adults with chlorpyrifos (Dursban), an organophosphate.

If the insects are mostly pupae, you should wait a week or ten days and then apply a pyrethroid, targeting the newly emerging adults.

In all cases, follow with a little water - one pass of the irrigation heads if you have good pressure, two passes if you have marginal pressure or it is a windy day (of course, if it is that windy, you probably shouldn't be spraying!). In the case of the pyrethroids, that is enough water to knock the material off the blades and into the thatch. Note that some of the manufacturers do not believe that post-application water on pyrethroids is necessary ... but personally, I prefer to see the applications watered in lightly.

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.