The non-weevil world seems to be pretty quiet so far in southern New England. Some of you may have seen damage from winter cutworms earlier in the spring, but they should be settling down. Several people reported that they had seen cranefly (leatherjacket) pupae emerging from the turf about three weeks ago (mostly in the southeastern part of the state), and saw adults flying at the same time. We can assume the summer generation of craneflies is now well underway in the areas where they have been active in the past.
But the annual bluegrass weevil story continues to be a confusing one. The weather so far this spring has been a contributor to the confusion. Attached are two graphs showing the accumulated growing degree days for Tumble Brook Country Club in Bloomfield, CT (about three miles northwest of Hartford). We have collected temperature data at this golf course every year since 2009, and the superintendent, Cindy Johnson, has provided turf samples every week during the ABW season, so we have lots of information over the past eight years.
The charts help us make sense of the conditions we have been seeing so far. In early April the degree days for 2016 were well ahead of the eight year "normal", and in fact it was the second warmest year we had seen in that period. But then cool temperatures set in and we did not accumulate any more degree days for a couple weeks. By the end of the month, the DD were right about in the middle for the eight year period. Temperatures have continued to be fairly cool through early May, and as of 16 May, 2016 is the third COOLEST year in the past eight years.
The dogwoods have been in full bloom for an extended period of time. Normally this marks the end of the period to apply an adulticide targeting the overwintering generation. Some superintendents reported seeing large numbers of adults on greens, tees, or fairways on warm sunny days in the past week. Dissections have confirmed that slightly more than half the adults on the fairways are reproductively mature, so I expect to start seeing larval activity fairly soon.
But in all the turf samples we have been receiving as part of our participation in the Weevil Trak monitoring system, we have still seen only first and second instars (TINY larvae that look like small weed seeds) in most locations. And to add to the confusion, the only place we have seen a few larger larvae (some third instars and one precocious fourth instar) is at our coolest site. By all conventional models, we would not normally expect to see those larger larvae at that site for another week or so.
Meanwhile overall the larval numbers appear to be much lower than they have been in previous years. I am not prepared to declare that this June will be an "easy" year because I have learned never to trust the weevils! I still suspect we will start to see an increase in larval activity as soon as we start to see some warmer weather. The forecast right now calls for temperatures in the high 70s and low 80s about a week from now, and I think we will get a much better sense of what is happening at that point.
Many of the Weevil Trak sites in southern New England are currently in Stage 2 (apply chorantraniliprole), but I suspect some of those will advance to Stage 3 (apply a larvicide) by the end of next week. The phenological indicator that works really well for that larvicide is Rhododendron catawbiensis full bloom.While we have not seen any evidence of buds opening yet, the warm weather at the end of next week should push them along.
So as said before, don't let your guard down yet!
Submitted by: Dr. Pat Vittum