Statewide Alfalfa Weevil Scouting Week 2

Is alfalfa weevil development out pacing your alfalfa’s ability to tolerate feeding pressure? As always, the answer to that question varies from field to field. Reports of alfalfa weevil across the state have some alfalfa weevils beginning to pupate to early stage infestations of very small, immature larvae. All of Ohio is firmly in the window of GDD where alfalfa weevils can be the most damaging (325 to 575 GDDs accumulation from a base of 48°F starting January 1^st).

In Table 1 are the scouting reports from around the state. It is worth noting that there is a fair amount of variation in the development of alfalfa across the state and size of the alfalfa weevil populations experienced. As seen in Table 2, alfalfa can handle a greater amount of feeding pressure as it grow and before the economic threshold for action is met.

Table 1: County alfalfa weevil scouting reports for April 20 – April 26

Table 2. Alfalfa Weevil Threshold Recommendations

With the early pressure observed, some fields have already been reported as sprayed. Before spraying, we recommend scouting to make sure that the application is a sound economic decision. Scouting is an easy process outlined in this ~4 minute video “Alfalfa Weevil Scouting”.

If a pesticide application is necessary the OSU/ MSU IPM Guide is a great resource for insecticide decisions. Prior to application be sure to read the label. After the insecticide application and the reentry interval is complete a scouting pass is a good practice to ensure sufficient control.