Alfalfa Growers Should Have A Good Sweep Net To Scout For Pests

ROCHESTER, Minn.— When it comes to managing insects in alfalfa, Bruce Potter suggests a heavy duty sweep net for scouting, one with replaceable parts.

"If you don't tear them up, you're not using them," he said Feb. 12 during Minnesota Forage Days in Rochester.

Potter, a University of Minnesota Extension integrated pest management specialist, said bugs enjoy alfalfa because it's a perennial crop, providing a more stable habitat than those in rotation.

Alfalfa weevils primarily cause damage in the first cutting and in re-growth of the second cutting. They can reduce yield and forage quality, destroy new seedlings and lower the overall stand health. Parasitic wasps were thought to be a good biological control, but now the weevil is becoming more of a widespread problem in the state.Growers should avoid using insecticide as insurance to maintain natural weevil enemies.

"In southeast Minnesota, it's something people should keep an eye on," Potter said during a telephone interview with Agri News.

Eggs are laid in spring at the base of stems. Larvae, with chewing mouth parts, molt four times and are active until mid-June. Pupae form cocoons at the plant's base and emerge as adults, which overwinter. One generation exists per year.

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