Potato leafhopper (PLH; Empoasca fabae) is a small insect that is easily overlooked until the damage called “hopperburn” starts showing up on plant leaves. Potato leafhoppers cannot withstand Wisconsin winters, and overwinter in southern states. The adults are blown up on wind currents into Wisconsin in May and June. PLH can feed on many different types of plant and so often doesn’t show up in apple until immediately after the first cutting of hay in the area – usually around mid-June. PLH adults are wedge-shaped, ~1/10” long and, have a greenish coloration. Both the adult and nymph potato leafhoppers move in a crab-like sideways manner. The PLH eggs are laid in the upper canopy of the tree, generally on youngw leaves or stems. The nymphs are smaller than the adults, orange/yellow-colored, and lack wings, although the later instars (stages) have wingpads. From egg to adulthood typically takes around 25 days, and there are generally two to three overlapping generations of potato leafhopper in Wisconsin.
Damage Symptoms. PLHs are most likely to affect young pre-bearing trees. They feed on the underside of foliage using a piercing/sucking mouthpart, and inject a toxin into the plant’s vasculature which slows water and nutrient movement. This can cause characteristic “hopperburn” where the edges of the leaves turn yellow and roll upwards. Hopperburn injury can resemble aphid feeding injury, so it is important to look on the underside of the leaf to identify the culprits. Additionally, potato leafhopper feeding damage has been shown to increase the prevalence of fire blight in an orchard, although the specific relationship between potato leafhopper and fire blight has still not been completely determined.
Monitoring and Control. Monitoring for curled leaves or shoots that are not growing vigorously can take place weekly beginning in June. If leafhopper damage is suspected, turn over the leaf slowly to be able to identify and count the leafhoppers on the bottom side of the leaf. No specific economic threshold has been determined in apple, but it is recommended to count nymphs on 4 leaves of 25 trees and apply insecticide when 1 nymph per leaf or when 30% of leaves sampled are infested with PLHs. It was mentioned that 1-2 PLHs per shoot can cause curling damage. In an orchard with a history of fire blight, control is recommended when a single potato leafhopper is identified in the orchard as PLH may vector fire blight. If located near a hay field, plan to scout more frequently around the hay cutting time as PLH may start moving into apples.
Chemical control. Several insecticides are available to control PLH in apple including reduced risk products such as Avaunt, Sivanto, Admire Pro, Actara, Assail; broad spectrum products, such as Baythroid, Imidan, Lannate; and Pyganic, Surround for organic production. For other affected fruit crops, be sure to read the label to make sure they are registered for that specific crop in Wisconsin. For more product recommendations please refer to the Midwest Fruit Pest Management Guide. Additionally, you should always fully read and follow the label before spraying any pesticide.
Happy growing season!This article was posted in Insects and tagged Christelle Guédot, hopperburn, insects, Leafhoppers, potato leafhopper.