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

Growth chamber and field studies indicate that initial potato leafhopp er feeding on alfalfa alters the plant's response to subsequent feedin g. Growth chamber comparisons made on different stems of the same plan t at a 72 hr interval had consistently higher damage ratings at the se cond insect exposure. Comparisons of different plants receiving one ve rsus two 72 hr insect exposures also showed greater damage on the seco nd exposure though differences were not as dramatic. Field trials on d ifferent plants supported growth chamber studies in that plants receiv ing two insect exposures had greater damage. Differences in the plant' s ability to recover from one versus two insect exposures were apparen t only in the same plant studies. A plant whose stem did not recover f rom the first exposure would be unlikely to recover from a second.