ACTION THRESHOLDS FOR POTATO LEAFHOPPER (HOMOPTERA, CICADELLIDAE) ON POTATOES IN MINNESOTA

The appropriate action threshold for application of insecticidal sprays to control potato leafhopper, E. fabae (Harris), on potatoes, S. tuberosum (L.), appeared to be approximately 10 nymphs/105 leaves. Applying treatments only when leafhopper populations reached 30 or more nymphs/105 leaves resulted in hopperburn and yield reductions. Treating for 10 or fewer nymphs/105 leaves necessitated additional spray applications of minimal incremental value in crop protection, but can trigger outbreaks of green peach aphid, Myzus, persicae (Sulzer). Only 2 spray applications were required when insecticidal applications were timed to coincide with peak nymphal populations in mid-July and mid-Aug. For these studies, essentially single species infestations of potato leafhopper were obtained by interplanting the potatoes with alfalfa strips [Medicago sativa, cv. Vernal].