You Are Here: Management Updates 2009 Archive May 29, 2009

Date: May 29, 2009
Category: Insects
Subject: Annual Bluegrass (Hyperodes) Weevil

Annual bluegrass weevil larvae are showing up all over the place now! For a while it seemed like they were off to a slow start, but the warm weather in mid May nudged all the populations into action. We have been collecting samples from several sites in New England and can report that larvae are growing rapidly now in all locations that we have been monitoring.

The results from samples pulled this week are as follows:

• Danbury, CT - evenly distributed between second, third, and fourth instars
• Bloomfield, CT - still some first instars but mostly second, third, and fourth instars
• Albany, NY - mostly third and fourth instars, but some seconds and some fifths
• Fitchburg, MA - mostly second and third instars

The interesting thing is that in many locations, the larval populations have increased quickly in the last week. Ordinarily we would expect areas that were mostly first and second instars last week to be mostly second and third instars this week, but the weevils seem to be getting bigger faster than expected right now. In several sites we saw mostly small larvae last week and are seeing mostly third and fourth instars this week.

So buckle your seat belts. It promises to be a wild ride this June.

We are at a point where any insecticide applications should be made to target larvae. According to the folks at DuPont, indoxacarb (Provaunt™) is most effective if it is applied just when the third instars become active in a given area. Ordinarily that would occur over a five to ten day period in most locations. Unfortunately, this year that window seems to have been about four or five days long in any given spot, and many areas in the metropolitan New York area and points further south have moved past that "window of opportunity". People in the Hartford area may also already be past that point now. We are still learning how best to use Provaunt™, and we really don't know how well it will work when it is applied when larvae are already third and fourth instars. We have some test plots out that will have the answer to that question in about a month.

My suspicion is that trichlorfon (Dylox™) might be a better bet if larvae are already fourth and fifth instars - but recognize that nothing will control 100% of the larvae once they approach full size. You will be doing well to achieve 75 to 80% control when targeting large larvae.

Some of you reported that you applied Provaunt™ a little earlier this spring and were concerned that you were seeing some small larvae in areas where you treated. We have noticed the same phenomenon. I think what is happening is that the tiny larvae spend their first week or two inside the stem and are not exposed to the Provaunt™ at that point, and then emerge to start feeding outside. They are perfectly healthy when they move outside (and I think that is when turf managers are seeing them). But they are still very small and vulnerable, and the chemical seems to kick in pretty quickly. So in several treated areas, we have noticed tiny larvae and a very few small third instars, but we don't see the larger larvae showing up. In other words, don't panic yet!!!

Stay tuned!

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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