The past week was relatively cool in most parts of PA, with only a few Growing Degree Days (GDDs) being accumulated. Our research sites in western and central PA accumulated 4 and 12 GDDs (Base 50 F) respectively, between April 22 and 28. Forsythia bloom has been hanging around full bloom for two weeks in State College (118 GDD as of 4/30) and at our monitoring site at the Bucknell University Golf Course (120 GDD as of 4/29).
We have seen a surprising amount of adult activity on the short turf despite the relatively few GDDs accumulated. Adults captured in vacuum samples were up substantially from the previous week at Bucknell, despite no real change in our plant indicators. Southeastern PA also showed the same trend: little movement beyond the 10-25% green Forsythia, but adult captures were on the rise. We were able to net a whooping 3400 weevils in 3.5 hours of vacuuming (of one edge of a Par 5!) on Monday. (The face of Danny Kline -master technician- shows the extent that our lab will go to get you your weevil data).
We were able to dissect many adults captured from various locations this week. The majority of males remain immature, though the percentage of mature males continues to tick upwards. Females are ready to drop eggs, but few (< 10%) were found to be mated. We will be continuing to monitor reproductive development and scout for egg in the next few weeks.
Based on the extended forecast I fully expect that many sites in PA will be at the 1/2 green and 1/2 gold stage by mid week next week. This is the ideal time to apply your adulticide.
I know that many people have been scouting with vacuums this year (Awesome! Echo- I need a sponsorship). Many have been startled by the amount of weevils they have detected. I fear that this “performance enhancing sampling method” has caused many to jump the gun and apply an insecticide. We sampled a couple of sites that had made an application a week or more ago. We did collect many dead weevils at these sites, but many, many more were alive. Pyrethroid resistance tests performed on these individuals produced negative results, indicating that the application did not last long enough to knock down the weevils arriving late to the game. If this sounds like your situation, consider holding off until 1/2 green 1/2 gold stage next year to make the most of your adult application. For now, dont make matters worse by following up with the same chemical class, and possibly think about targeting larvae instead.