You Are Here: Management Updates 2005 Archive June 14, 2005

Date: June 14, 2005
Category: Insects
Subject: Annual Bluegrass (Hyperodes) Weevil

Bumpy road ahead for Hyperodes weevil control!
Many superintendents are reporting they are seeing all different stages of Hyperodes weevils (annual bluegrass weevils), all at the same time. We have had the same experience. In fact, in some of the two inch cores we collected last week in Westchester County (just north of New York City), we had small larvae, medium larvae, large larvae, and pupae all in the same plug!

I think this year will prove to be one of the most challenging for golf course superintendents battling ABW. Most years the adults become active at about the same time in a given location so there is a three or four week period during which females lay eggs. Then the larvae develop at about the same rate, and we can kind of guess what will happen next. This year it appears that egg-laying
was spread over at least six weeks, perhaps even more. That means that we already have a wild combination of stages occurring at the same time and it is already difficult to figure out how to manage the damage.

Reports from south central Pennsylvania indicate that most of the insects are pupae or young adults (still tan or rust colored). Plugs pulled from Westchester County last week revealed mostly large larvae and just a few pupae. I assume there are more pupae showing up now, along with the "laggard" larvae that just hatched a couple weeks ago. Most folks in southern New England are about a week behind that, so you should be seeing wilting in areas where larvae are feeding actively.

As a reminder, the treatment options are roughly as follows:

A. If sampling shows that most of the insects are still larvae, you may get some relief by spot treating with trichlorfon (Dylox™). ABW is now on the Dylox™ label (approved by EPA over the winter), but not all states have accepted the new label yet.

B. If most insects are pupae, wait a week and use a material that will stay in the thatch (a pyrethroid or Dursban™). (Pupae are not vulnerable to insecticides so you need to wait until they emerge as adults.)

C. If most insects are adults, treat with a pyrethroid or Dursban™ as soon as convenient. This application remains in thatch and should kill many adults before they have a chance to lay eggs

While the hot weather pattern is scheduled to break very soon, keep in mind that most pyrethroids are very sensitive to high temperatures and can be less effective when applied in extreme heat. So it probably is wiser to wait until the cooler weather comes, or at least treat very early in the morning before temperatures climb. And remember to water in lightly (one or two passes of the irrigation head).

Frankly, I suspect many golf course superintendents will be playing "catch up" all year. Those who are managing courses with a history of ABW activity may well be spot treating all summer long.

Based on conversations with superintendents, I think the ones who got better control with their spring applications were those who waited a little longer into the spring and treated closer to serviceberry or dogwood full bloom. And some of our field trials this spring are indicating that pyrethroids don't last forever! We are finding that plots treated with a pyrethroid (in late April) have few or no large larvae but there are some small larvae showing up in those plots. All I can figure is that the residual activity was not sufficient to knock out the "laggards" from this crazy spring.

Condolences to all of you - it will be a bumpy road this year. Feel free to stay in touch, either by e-mail or by phone (413-545-0268) and let me know what you are seeing. Sharing that information helps everybody

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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