Agronomic Insect Update – May 4, 2018

David Owens, Extension Entomologist,

Continue scouting alfalfa for alfalfa weevil damage. With the warm weather we have been having, they are active state-wide. When sampling, collect 30 stems (stems should be taken from several locations in the field), and beat bundles of 5-10 stems to dislodge larvae. Thresholds for alfalfa weevil depend on the number of larvae found, the growth stage of the plant, and the size of the plant. Early harvest may be an option. We have a video demonstrating weevil sampling: an alfalfa weevil fact sheet for thresholds and decision making: and finally, insect control recommendations here:

Grain Crops
David Owens and Bill Cissel
Virginia has started seeing large numbers of brown stinkbugs in small grain cover crop and production fields. Stink bugs are not a pest of small grain, but will put their first generation into small grain. Where this becomes a potential concern is later in the season when wheat is harvested and the stink bugs need to go elsewhere. Corn is not susceptible to stink bugs until V3-V4, when the growing point moves out of the soil.

Cereal leaf beetle activity has picked up recently, though I have not yet heard of a field at threshold. Continue scouting your fields. Virginia reports that true armyworms have not been very active yet, and we have only picked up a couple of moths in light traps. Sawflies are just starting to be active. Pay attention to the number of legs. Sawflies have legs on every segment, they are active on plants during the day, and the threshold for them is half that of armyworm. More information can be found in our small grain recommendation guide.