University of Illinois

No. 17/July 18, 1997

Alfalfa and Oats and Leafhoppers: What Can Be Done?

During the past week, I received about a half dozen telephone calls concerning severe infestations in alfalfa intercropped with oats. The infestations of leafhoppers were so severe that the alfalfa had turned completely yellow and then red-purple, and some of the plants were dying. However, the oats were still 2 weeks from harvest. The obvious question was "What can I use to control the leafhoppers on the alfalfa that is also labeled for use on oats?"

After reviewing our recommendations and a few insecticide labels, I have determined that the only two products labeled for leafhopper control in alfalfa and labeled for use on oats after the heads have emerged are malathion and Penncap-M. Both products are reasonably effective for control of potato leafhoppers, but malathion will not provide long residual. Furadan 4F is labeled for use on both alfalfa and oats, but it cannot be applied after the oat heads have emerged from the boots. The harvest intervals (the limitations in days between insecticide application and crop harvest) for malathion and Penncap-M are 7 and 15 days, respectively.

Kevin Steffey, Extension Entomology, (217)333-6652