It is time to start scouting for alfalfa weevil feeding in alfalfa stands across most of the state. Peak alfalfa weevil feeding damage occurs between 325 and 575 heat units (based on accumulation of heat units from January 1 with a base of 48°F). We have been following the accumulation of heat units in several regions of the state, and the current accumulations are shown in the figure below. Locations in red are in the heat unit range when we expect peak larval feeding, and locations in orange are getting close to the peak activity range. Now is the time for most alfalfa growers to step up their alfalfa weevil scouting. The cold weather will hold back alfalfa growth, which could result in more damage by weevils present. For more details on alfalfa weevil scouting and thresholds please click HERE for our April 13 article, as well as this VIDEO describing how to scout a field.
Accumulated growing degree days (base 48°F sine calculation method) for January 1-May 3*, 2020 at several CFAES Ag Weather System (https://www.oardc.ohio-state.edu/weather1/) locations and additional NOAA stations around Ohio. *Ashtabula through April 30