Annual Bluegrass Weevils: On the Move
The winter in Massachusetts was unusually warm, with a departure from average of 3-5˚F throughout the state each month from December to February. Spring so far has been a roller coaster of warming-up and cold spells. In addition, March and April have been wetter than normally observed. An accumulation of degree days occurred in the second week of March and then again in April. Most of our monitoring sites have accumulated 20-30 GDDs at this point, although our coastal site had only 5 GDD last week. Forsythia is in full bloom or close to full bloom.
We started monitoring weevil activity in early March and observed movement from roughs starting at the end of March. The first weevils were collected from fairways during the first week of April at all sites, except the coastal site, which, again, is behind western MA sites this year. Because of the unusually warm winter we expected ABW activity to be early, however we have seen a low number of ABW adults, which is so far is about a week later than last year. We observed low adult and larval densities of ABW in the region in 2023, and that also might be influencing population densities this year. Low numbers of adults this year might also be a reflection of the very wet conditions and relatively cool spring.
According to the forecast for next week, we are expecting a significant warm up for much of southern New England, which will result in increased GDD accumulation and weevil activity next week. Adult activity will be most likely to pick up with expected warmer temperatures during the following week. We are expecting a relatively synchronized adult emergence, with the peak arriving in one or two weeks.
Thus, we are getting very close to the point of adulticide application in many locations, but managers should hold until the following factors come together: adult activity increases, GDD accumulation is near 100, and Forsythia or Bradford pear are "half-in-bloom, half-green". It is a good time to start monitoring for ABW adults using soap flushes, vacuuming, visual inspections of greens, and checking clippings collected from greens.
Remember that even if you start seeing adults on the surface, resist the temptation to use an adulticide before that magical Forsythia "half green-half gold" timing, when adults are peaking. The adulticides (pyrethroids) have a short residual and the timing has to be precise for this application to be effective. A new insecticides, novaluron (SupradoTM) has been shown to be very effective if applied at the adulticide timing, however it has a wider window of application and can still be effective if applied during the oviposition and young larvae stages.
White Grubs
As soil temperatures approach 50 ̊F, grubs are expected to resume activity and feeding very soon. Based on this week's sampling, the grubs were still at about a 3-4” depth. Next week will be a good time to monitor white grub populations to inform decisions for grub management during the upcoming summer. Curative applications for grubs in the spring are usually not recommended, unless severe damage is occuring to highly valuable turf.
Other Pests
Wet springs usually do not favor chinchbugs, because increased mortality typically occurs. This happens in part because of a naturally occurring fungus, Beauveria bassiana, which thrives when springs are wet.
The wet conditions might favor craneflies, however. Flight and egg laying for common craneflies are expected at the end of April – beginning of May.
Submitted by: Dr. Olga Kostromytska