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Management Updates: Apr 19, 2017

Annual Bluegrass Weevils
Apr 19, 2017

Many golf course superintendents in southern New England are wondering what all the mixed messages mean regarding the movement of annual bluegrass weevils (ABW). The "mixed messages" started with unusually warm temperatures in late February, which might have induced some of the adults to start moving out from their overwintering sites. But then the temperatures turned markedly cooler for most of March, enough so that apparently the average temperature for March was cooler than the average temperature for February. That's pretty mixed up!

April temperatures remained on the cool side until about a week ago, and in spite of some heavy rains earlier in April, the soils were on the dry side in many locations a week ago. Just a little bit of rain and more moderate temperatures over the Easter week-end suddenly provided the jolt that got things moving.

So all of a sudden the daffodils and Forsythia are in full bloom in Amherst, and several of the ornamental spring bloomers are showing their colors. Star magnolias exploded into full bloom after receiving a little bit of rain. I did a double take earlier today when I saw a white dogwood starting to bloom on the campus, and some of the PJM rhododendrons started blooming in the last couple days as well.

As usual this kind of rapid change in plant phenology brings a certain level of "angst" to golf course superintendents, and I suspect many are tempted to get out there and "do something" to control the ABW. One of the keys to success in managing the weevil is knocking down a significant number of adults that are coming out of overwintering. If they all got on the same train and left their overwintering sites together, that would be easy - but they don't! So there are always some individuals that are quick to start moving, and others that take their sweet time.

Remember that most of the weevils you might see moving on the fairways in the next few days are NOT reproductively mature. The object of a spring adulticide is to kill adults before they have a chance to lay eggs, but many studies conducted throughout the region confirm that it is most efficient to wait until you see "peak adult activity". Superintendents in the DelMarVa region are reporting that peak activity now, and it seems to coincide with the usual Forsythia "half green-half gold" indicator. Another plant that seems to be serving as good indicators this spring is the eastern redbud. These indicator plants are the prod to remind you to get out and look for adult weevils on the short grass on sunny days. You can use a soapy flush or a vacuum sampler or just get down on your hands and knees and take a good look at your usual hot spots.

But remember that for many of you in New England, it is still too early to send that sprayer out with the pyrethroid or chlorpyrifos. And temperatures at least in the Amherst area are projected to be on the cool side for the next week or more, so hang on a little longer! All indications are that we are still at least a week away from "peak adult activity" in Amherst.

Submitted by: Dr. Pat Vittum