You Are Here: Management Updates 2004 Archive April 30, 2004

Date: April 30, 2004
Category: Insects
Subject: Annual Bluegrass Weevil Update (golf course only)

Annual bluegrass weevils are on the move. As the weather has finally begun to warm up, we have received reports from several superintendents that weevil adults are active on the surface. Here is a quick review of the most pertinent points to keep in mind.

Spring applications normally should be made after Forsythia has reached full bloom. I often suggest that superintendents wait at least until Forsythia is in what I call the "half green - half gold" stage (the golden blossoms are still apparent but many of the new young leaves are showing as well). Many people wait until dogwood is in full "bloom". This year the timing has been a bit confusing because Forsythia has been in full bloom for several weeks in some locations, and the cool temperatures of the spring have slowed development of trees and shrubs - and insects! The main point is that it is usually better to be a little bit "late" than a little bit "early" with the spring application.

I just returned from a trip to Westchester County, New York. On one golf course I saw Forsythia that had gone completely past bloom, so all that was showing was the new leaves. Other parts of the course were about a week behind. And three miles away, on a highway median, Forsythia were just approaching full bloom, at least two weeks behind the leafy Forsythia. In parts of southern New England, Forsythia are just beginning to show some leaf development. So timing of application will vary widely this year - use the nearest Forsythia plantings to help figure out your local conditions.

Many superintendents apply an insecticide to the greens and collars (and, if past history warrants it, tees). In most cases, widespread fairway applications are not necessary. Particularly in the spring, fairway damage usually is restricted to the edges of fairways, so perimeter sprays of the vulnerable fairways should be sufficient. While annual bluegrass weevils will feed on some bentgrasses, they still strongly prefer annual bluegrass.

The insecticides that seem to be most effective against annual bluegrass weevils in the spring are materials that remain in the thatch ... such things as Dursban™ and the pyrethroids (Battle™, Scimitar™, Talstar™, Tempo™, and Deltagard™). In most cases a single application should work very well. Water in lightly (one or two passes of the irrigation head), just enough to get the material off the blades and into the thatch.

So far there are no non-chemical control agents that are available commercially that have also demonstrated consistent reduction of weevil populations. We will continue to look for non-chemical options but for now, traditional insecticides are the only viable alternative. In the meantime, continue to concentrate on the cultural things, in particular reducing the amount of annual bluegrass in critical areas.

- 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.