I have received many questions this week about annual bluegrass weevils (or Hyperodes weevils). Many of you are wondering what is going on with weevil development this year. Here's how I see it. (Keep in mind this is strictly a golf course problem.)
We collected several turf samples on Monday, 2 June (a week ago) from a golf course just north of the Tappan Zee Bridge in New York. When we went through those samples, we found some eggs (thanks to a new technique shown us by the folks at the New York Experiment Station in Geneva, most notably Nancy Consolie). We also found very small larvae, middle sized larvae, and large larvae. I suspect most of the egg-laying is finished now in Westchester County and the rest of the metropolitan area, and I suspect most superintendents in that region will start to see the characteristic wilting from larval feeding early next week (the week of 16 June) - especially if the weather ever begins to dry out.
The development we saw in the field last week is about a week (or maybe even two weeks) behind "normal". It is too late to apply an insecticide to target adults, since they have already laid most of the eggs. However, for those of you who have the option, you could consider applying a fast-acting and mobile insecticide as soon as you see the small larvae feeding. (The larger larvae look like grains of rice and will be found in or just above the crown of the plant.) Note that the annual bluegrass weevil is NOT on the label of all turf insecticides, and it is "let the applicator beware". The pyrethroids do NOT seem to be very effective against larvae.
For those of you in areas north of the metropolitan area, you can expect weevil development to be about a week (or more) behind that described above.
At this point my best GUESS for applications of insecticides to target adults of the second generation would be the week of 7 July (or later) for the metropolitan area and a week later than that for locations further north. Note, however, that this is a GUESS and will be refined in coming weeks as we see what the weather patterns (and most notably daily highs and lows) are in late June.
Stay tuned for further developments! And, as always, good luck dealing with the "little monsters".
Submitted by: Dr. Pat Vittum