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Management Updates

This section of the web site features Management Updates written by the turf specialists of the UMass Extension Turf Program. The messages cover regional problems, are geared toward regional conditions, and are posted frequently during the growing season.

The most current message appears below; click into the archive to see messages from the current and previous growing seasons.

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Annual Bluegrass Weevils, White Grubs

Apr 18 2019

Spring is springing!

As the temperature finally begins to warm up, we are beginning to see Forsythia blooming, along with star magnolias and daffodils, in the Pioneer Valley. For those of you on golf courses, you know that means that annual bluegrass weevils will be on the move soon. In fact, some superintendents are already reporting adults in their pitfall traps. Adult weevils have been extracted by soapy flushes along the edges of fairways.

The temptation, as always, is to go out and apply an adulticide as soon as you see adults moving on the fairways, greens, or tees. But research over the past several years has shown that most adults take at least a week or two to reach reproductive maturity after they reach the short grass. And the adults move over a period of time, so while you may be seeing some adults on the surface (or in the greens mower baskets), there will be more adults leaving the overwintering sites over the next couple weeks. The adulticides we currently have available (pyrethroids and chlorpyrifos, for the most part) have a fairly short residual, so if you apply the product too early it will break down before all the adults arrive on the short grass.

So this is our annual reminder to wait at least until the Forsythia in your area have reached the "half green-half gold" stage. Another plant indicator that seems to work most years is Bradford pears - wait until you start to see a little green after the full bloom of the pears. Most of the sites in the area accumulated only up to 50 growing degree days (base 50), while adulticide application is optimal at 100-120 GDDs. Applying earlier than that usually leads to disappointment. It is time for the careful monitoring of ABW adult activity. Soap flushes and vacuum sampling on fairways will help to detect the buildup of weevil activity and pinpoint the timing for management efforts.

Now that soils are beginning to warm up, we can expect white grubs to make their way back to the root zone. Start monitoring in areas where you saw grub activity last fall. Keep in mind that the wet conditions many experienced in the summer and fall may have masked grub activity, so you may have had moderate populations and not known it. If we have a dry spring (which so far seems unlikely), you could experience some damage from grubs this spring.

Submitted by: Dr. Olga Kostromytska and Dr. Pat Vittum