Action Thresholds for Potato Leafhopper on Potatoes in Minnesota12

The appropriate action threshold for application of insecticidal sprays to control potato leafhopper, Empoasca fabae (Harris), on potatoes, Solanum tuberosum (L.), appeared to be ca. 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 which 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 inter planting the potatoes with alfalfa strips.