INSECT PROBLEMS IN NEW STANDS

Defoliating caterpillars can thrive with mild weather and limited moisture. In seedling alfalfa, these pests (e.g.. webworms, cutworms and fall armyworms) can quickly devastate a young stand. Populations as low as two caterpillars per square foot can significantly thin alfalfa. Producers should be encouraged to closely watch seedling alfalfa stands, particularly around grassy field borders where these pests may initially build up.  

Spotted alfalfa aphids can be persistent in any growing season, and producers with seedling stands should constantly watch for the presence of these tiny yellow aphids. Because these aphids inject toxins into the plants during feeding, low populations (1-5 per stem) of spotted alfalfa aphids can kill seedling alfalfa.  

In the late summer or early fall, Grasshoppers can occur in high numbers around grassy areas. Where grasshopper habitat is next to a newly sown alfalfa field, they can devastate field margins and sometimes move well out into the alfalfa. Producers should scout such areas frequently and treat before alfalfa seedlings are completely gone from margin areas.  

When aphids, grasshoppers, or caterpillars require chemical treatment, several compounds are available, including Lorsban^®, Parathion, Pounce^® and Malathion. Choice should be based on cost and the restrictions involved with using each compound. Many producers use Pounce^® at 0.15 lb. a.i./acre with excellent results. Some applications for these insects are unnecessary, particularly late in the fall, because freezing weather eliminates the problem.