Spring has officially sprung and now is a good time to start thinking about the insects that will be emerging and subsequently feeding on alfalfa, particularly alfalfa weevil.
Alfalfa weevils are beetles that overwinter primarily as adults and emerge as temperatures warm and begin to lay eggs. Plant injury from feeding damage initially appears as pinholes in the terminal leaves, with leaves becoming skeletonized as feeding severity increases.
Alfalfa weevil was responsible for significant damage to some fields in 2024, particularly in central and eastern Nebraska. Producers should begin scouting for this insect in early April or when spring growth begins.
To scout, randomly select 5 sites across the field and collect 10 stems at each site, cutting the stems at ground level. Beat the stems into a deep-sided white bucket and count the number of larvae to determine the average number per stem. Larvae are around 8 millimeters long with a black head, wrinkled green body and white stripe running lengthwise along the top. A threshold table that includes alfalfa as short as 4 inches can be found on the Iowa State Extension website at tinyurl.com/4334rbpj.
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 recently reported in several western states. Therefore, if you believe you have an infestation above threshold, contact your county Extension office for further guidance. — Samantha Daniel, Nebraska Extension
