Potato Leafhopper, Empoasca fabae Harris

I. Introduction: Potato leafhopper (PLH) is a pest mainly of young apple trees. The nature of injury and phenology are quite different from the WLH.

II. Hosts: PLH has a wide host range. It is a pest of alfalfa and potato in our region, in addition to apple, grape and other species.

III. Description: Adults and nymphs are both green in color (Plate 62). Legs are spinier that WLH. There is a series of six white spots on the pronotum (the shield immediately behind the head). This species is more active on the leaf than WLH. Nymphs will run sideways, quickly running to the other side of the leaf as the leaf is examined.

IV. Biology: PLH overwinters in the Gulf Coast states, and must reinvade the mid-Atlantic region each spring. Adults reach Virginia in mid-May to late June. Adults are the first stage seen. Nymphs resemble small adults without wings. This species, unlike WLH, has a toxic saliva which causes xylem and phloem tubes to collapse, causing the inability of water and nutrients to reach the leaf and of photosynthates to leave the leaf. There are several (usually 2-4) overlapping generations. Nymphs emerge until mid-September and adults are present until mid-October in Virginia, although densities are usually very low by this time because of the lack of young leaves.

V. Injury: The cellular injury caused to the leaf of the various food plants causes a typical "hopperburn" (Plate 63). Unlike WLH, PLH prefers young leaves, where it feeds on vascular tissue, and consequently is a greater problem on young trees, which have a greater proportion of young leaves on each tree, and continue growing longer into the season. Invasion and resulting damage can occur quickly. The edges of the leaf curl downward, first turning lighter green, then yellow, and finally brown and necrotic. On young trees this may be sufficient to stop growth of the tree. If these leafhoppers are controlled, growth may resume later in the season.

PLH has been shown to be able to increase infection by fire blight in young shoots.

VI. Monitoring: Young blocks should be frequently inspected from mid-May. Weekly sampling may be insufficient. Experience has shown that adults may invade in sufficient numbers to initiate hopperburn in the interval between two weekly scouting visits. No threshold is currently available. Consider treating when adults first appear in young blocks, especially if PLH has been a problem in the area in the past.

Additional Reading:

This is taken primarily from a chapter by D.G. Pfeiffer, L.A. Hull, D.J. Biddinger, & J.C. Killian on apple indirect pests, reprinted with permission from Mid-Atlantic Orchard Monitoring Guide, published by NRAES, 152 Riley-Robb Hall, Ithaca, New York 14853-5701.
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