By Samantha Daniel
The incredibly mild winter we’ve experienced this year has accelerated the accumulation of growing degree days for one of our most significant forage pests: the alfalfa weevil. For example, areas in southwestern Nebraska have accumulated an average of 318 growing degree days compared to 134 at this time last year. In addition, Kansas State University recently announced that weevils are already active in Kansas (https://eupdate.agronomy.ksu.edu/article/alfalfa-weevils-are-now-active-in-kansas-685-5 ). These factors indicate that early scouting for alfalfa weevil is critical this year.
In Nebraska, alfalfa weevil scouting is generally recommended once 200 growing degree days have accumulated. The western half of the state west of U.S. Highway 281 is at or well beyond this mark and the eastern half of the state isn’t far behind. Alfalfa producers are urged to begin scouting now, especially in fields that have broken dormancy. For fields that are still fully dormant, feeding damage from alfalfa weevil is less of a concern because they require green, growing foliage to thrive.
While there are several insecticides labeled for alfalfa weevil management, in Nebraska there have been reports of some products not performing as well as expected and resistant alfalfa weevil populations have been reported in several western states. Therefore, if you believe you have a significant early season infestation, contact your county Extension Office for further guidance.