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Management Updates: April 24, 2023

ABW Adult Peak, White Grubs, Chinch Bugs, and Billbugs
April 24, 2023

Peak of annual bluegrass weevil adult activity

Temperature patterns In Massachusetts have been a roller coaster ride for a couple of weeks. After a relatively cold start, daytime high temperatures across the region reached the 90s during April 13-14 before dropping back to daytime highs in the 50s and 60s. By the end of last week (April 20-21), temperatures edged up again, but are expected to be low this week. Despite such fluctuations, all indications confirm the current peak of ABW adult activity in the region. According to our observations in Northern Connecticut, Western Massachusetts and near Albany, NY, the adult peak started during the week of April 17-21, and during the week of April 24 – 28 in the Boston area. If an adulticide application is included in your ABW management program, now is the time in our region.

Our predictions and estimations are based on GDD accumulation, plant phenology, and adult sampling (vacuuming). As of April 11, the GDD accumulation was low (40-60) and Forsythia had barely started blooming, but the weevils were active and steadily migrated to the short cut grass. In one week, however, GDDs have been accumulating rapidly… reaching up to 120-130 GDDs across the region. Forsythia is now perfect half green/half gold. Adult numbers are peaking on the short cut grass, and only a few adults were collected on the roughs, suggesting the end of migration from the overwintering sites.

Once again, all indicators are now aligned, suggesting a peak of ABW adult activity. It is important to mark this time even if an adulticide application is not planned, as it can be a “biofix’ or point from which further larval activity can be predicted. Roughly two weeks after adult activity, small larvae are expected to feed inside of the plant (around late bloom of dogwood, ~200- 250 GDDs). This season we have observed slightly early (~1 week) adult activity.

White grubs

Soil temperatures are increasing and now average 46-47° F across the region. Grubs have been found at an average depth of 1.5” and have resumed their feeding. At high densities, some damage can be observed, which is caused directly by grub feeding and/or large predators digging for grubs (secondary damage).

It is usually not recommended to make applications targeting the large larvae feeding in the spring, because this approach is not very effective. In addition, grubs will be pupating soon and therefore chemical application is often unnecessary. If grub feeding is noticed in the spring, the best course of action is to schedule a preventive application of either a systemic anthranilic diamide (chlorantraniliprole) or a neonicotinoid (imidacloprid and clothianidin). If chlorantraniliprole (AceleprynTM) application is included in the grub management program, the best timing for this application is between April 15 – June 15, but this application will target grubs which will hatch in the summer and is not likely to affect the large grubs feeding in the spring. For more info on preventive management of white grubs, see

Note that neonicotinoids recently becamerestricted used materials in Massachusetts. Neonicotinoids also have activity against pollinators, so they cannot be applied on blooming plants, including weeds. The best timing for neonicotinoid application is during egg laying starting the last week of June through the beginning of July, even though the target is small larvae which will hatch later in the season. For more info on reducing potential impacts of neonicotinoids on pollinators, see

Chinch bugs and billbugs

We collected the first adults of chinch bugs and billbugs last week. We continue to monitor their activity and expect the peak of billbug adult activity during late May. Chinch bugs are expected to reach the nymph stage during June.


Submitted by: Dr. Olga Kostromytska