Update on insect activity on alfalfa and wheat
Alfalfa: Weevils, aphids, and army cutworms
Alfalfa weevils have been hatching from eggs in north central Kansas since at least March 13, when we first detected larvae. Since then, again in north central Kansas, the larvae are slowly growing and eggs continue to hatch. However, both alfalfa and larvae are growing slowly so far. Alfalfa weevil development occurs at, or above, temperatures exceeding about 48 degrees F. It is a different situation in south central Kansas, however. Producers there have been spraying pea aphids for a couple of weeks now and some fields have had to be treated for army cutworms (see photo). Keep in mind any fields treated with an insecticide will have the beneficials eliminated. As the alfalfa puts out new foliage it will not have any insecticide residue. As more aphids, or other pests, migrate into these fields there won’t be any beneficials (e.g., lady beetles, lacewings, and parasitic wasps) to help control them and there may be new untreated foliage for pests to feed on. So, it will probably be good practice to resume sampling 2-3 weeks after an insecticide application.
Wheat: Aphids and mites
We started finding a variety of aphids in wheat this week in south central Kansas, as well as a few aphids in north central Kansas. Aphids identified from samples brought in from south central Kansas included greenbugs, bird cherry oat, English grain, and corn leaf aphids. The colonies appear to just be getting started as there would be one winged adult with 3-4 small nymphs and only about 10% of the tillers were infested. No lady beetles were detected yet. A few winter grain mites (see photos below) were also observed but not in numbers to be concerned with.
Jeff Whitworth, Extension Entomology
Holly Schwarting, Entomology Research Associate