Annual Bluegrass Weevil (ABW)
All indications are that the 2026 season will be yet another challenging season for ABW management. The 2025-2026 winter was relatively harsh in New England, however the accumulation and persistent snow cover might have alleviated the negative effect of low temperatures on populations of ABW and other insects. To heighten the challenge, this spring has been a roller coaster with sudden spikes of unusually high temperatures followed by the cold spells. This has resulted in relatively high accumulation of GDDs, however this increase has been sporadic with long periods of no accumulation. Differences among the sites we monitor are pronounced more than usual this year, therefore it is important to monitor weather and GDDs closest to your area.
The GDD accumulation so far ranges from 31 to 117 GDDs, with 117 GDD in Connecticut, indicating almost a peak of adult activity in this area. In Eastern MA and Cape Cod, the accumulation is the lowest (31-40). The ABW adult activity and plant phenology are lagging at these areas compared to western MA, and CT.
Forsythia is now in full bloom, therefore it is time to start paying close attention to ABW adult activity. Soap flushes, vacuuming, visual inspections of greens, and checking clipping buckets after greens mowing can be used to detect peak densities of adults. Monitoring adult activity is a valuable investment of time and effort even adulticide application (pyrethroids and novaluron are recommended during this time) is not in your plans. The peak of adult activity is a reference point for early larvicide application, which ideally should be scheduled 1-2 weeks after the adult activity peak (anthranilic diamides and novaluron are recommended at that time).
We have been monitoring weevil activity since early April. ABW adults started appearing on short grass in the first week of April in CT, and but not until mid-April in Western MA. No adults were found on short grass in Eastern MA and Cape Cod golf courses. According to our observations, the overall densities and activity of ABW adults were not dramatically affected by the winter and spring weather, however there is a risk of prolonged and asynchronous adult emergence. We are getting very close to the point of adulticide application in many locations, but we are still waiting for when the following factors come together: adult activity increases, GDD accumulation is near 100, and Forsythia or Bradford pear is half-in-bloom-half-green. At the same time, we are expecting another dip in temperatures which might prolong the adult emergence and make it challenging to come up with any meaningful predictions and to pinpoint the optimal adulticide timing. In general terms, the peak of adult activity is expected within the two weeks, depending on location. It seems it is easier to focus on larvicide application this year.
Other Insects
The hot and dry weather we’ve had this spring is favorable for the buildup of chinch bugs populations. With weather fluctuations it is hard to predict whether the dry conditions will persist, but as for now chinch bug adults are already active in the grass and relatively abundant.
Our two-year study on chinch bug phenology demonstrated that the activity of chinch bugs varies highly from season to season, and during “unfavorable” years (wet spring), the populations can naturally collapse without an intervention. Therefore, it is important to monitor chinch bug populations, especially in areas with history of chinch bug infestation/damage. We have been monitoring chinch bug activity using vacuuming and pitfall traps. During the first week of April, we observed active adult chinch bugs in our samples for the first time this season. Nymphs are expected to appear and peak by the end of May.
Billbugs are expected to show up in May with adult activity peaking during the last week of May. But as for now they are not active yet.
The soil temperature reached 50°F, and as expected, white grubs moved closer to the surface and resumed feeding. Interestingly, our soil sampling has proven that white grubs are active throughout the region, and their activity seems to be not so strongly correlated with GDD accumulation (if air temperature is measured). Commonly it is not recommended to treat grub infestations in the spring, even though some damage might occur (unless it is absolutely critical to stop the damage). The environmental conditions during recent years were conducive to high-density grub populations, therefore the risk of some visible damage in the spring is elevated this season. Keep in mind that applications of chlorantraniliprole (Acelepryn TM) is recommended from April 15 to June 15. However, this application is preventive, and targets grubs which will hatch in the summer. It provides little to no control of the large third instar larvae feeding in the spring before pupation.
Submitted by: Dr. Olga Kostromytska, Extension Assistant Professor, UMass Stockbridge School of Agriculture