As I feared, the ABW season is on us "fast and furious". I have received several phone calls last week and today from golf course superintendents throughout the Northeast reporting that they are seeing more severe damage than they have seen in several years. My best guess is that the heavy snowfall over the winter (and generally shallow frosts in many places) produced conditions to their liking.
In addition the steady rains of the spring have masked some of the larval activity up until the very hot temperatures that dominated the region last week.
In a test pulled last Wednesday (8 June) near Danbury, CT, we had the following breakdown of developmental stages:
- 7% second instars
- 17% third instars
- 23% fourth instars
- 23% fifth instars
- 12% prepupae
- 18% pupae
- 1% overwintered adults
The good news in this situation is that by that time, 30% of the insects were no longer feeding. The hot weather that followed undoubtedly sped up the development of the medium-sized larvae (the third and fourth instars), so they are probably almost done feeding now as well.
The disheartening thing is that there is such a spread of developmental stages. We have been dissecting weevils throughout this spring, and most of the females collected from just southeast of Hartford, CT last week still had at least a few eggs in their bodies.
So this year seems to be producing a "perfect storm" for ABW development. Apparently the winter conditions did not result in much natural mortality. And for whatever reason, the egg-laying period this spring has persisted for at least five weeks, at least at the courses we are monitoring in New England.
What next??? If you take samples and find that half the larvae are still third instars or smaller, you should get some relief by using a larvicide. Remember that the look like grains of rice with brown heads. The third instars are less than 1/16 inch long.
If most of the critters you find are prepupae (they look like larvae and are about 3/32 inch long but do not have any black spots on their "backs") or pupae, they are done feeding and the worst should be over for now. The trick is to wait for about two weeks and apply an adulticide at that time. That would be very close to the traditional "Fourth of July" application that has often worked well over the years.
Monitor aggressively from now on. This promises to be a wild ride, indeed.
Submitted by: Dr. Pat Vittum