RESPONSE OF ALFALFA, MEDICAGO-SATIVA, L, TO SEQUENTIAL FEEDING BY THE POTATO LEAFHOPPER, EMPOASCA-FABAE (HARRIS) (HOMOPTERA, CICADELLIDAE)

Growth chamber and field studies indicate that initial potato leafhopper feeding on alfalfa alters the plant's response to subsequent feeding. Growth chamber comparisons made on different stems of the same plant at a 72 hr interval had consistently higher damage ratings at the second insect exposure. Comparisons of different plants receiving one versus two 72 hr insect exposures also showed greater damage on the second exposure though differences were not as dramatic. Field trials on different plants supported growth chamber studies in that plants receiving two insect exposures had greater damage. Differences in the plant's ability to recover from one versus two insect exposures were apparent only in the same plant studies. A plant whose stem did not recover from the first exposure would be unlikely to recover from a second.