There are several species of leafhoppers that are pests of apples: white apple leafhopper, rose leafhopper, and potato leafhopper. Potato leafhopper is a migratory pest that commonly attacks alfalfa in early summer, but on occasion, can be a serious problem in apples, particularly with young trees in new plantings. This past week I had a report of very high numbers of white apple leafhopper in a small orchard with significant damage to the leaves.
White apple and rose leafhoppers feed with piercing-sucking mouthparts to remove cell contents and sap from leaves. The damage can look very similar to mite damage, as they feed in the same way. The result is stippling of the leaves, that is, tiny light colored patches on the upper leaf surface (Figure 1). Damage is caused by nymphs and adults removing chlorophyll and sap from the lower leaf surface, which also affects fruit development and bud formation. Potato leafhopper is less common and is characterized by yellowing and necrotic leaf margins. While these damaged areas are typically V-shaped, intense feeding can cause the entire leaf margin to be affected.
Juveniles are generally pale white, wingless, and they “scurry” around when disturbed. While white apple leafhopper nymphs are without noticeable markings, older rose leafhopper nymphs have a few small black spots on the black of the thorax and wingpads. Potato leafhopper is light green.
Potato leafhopper can be distinguished from white apple leafhopper by the tendency of white apple leafhopper to walk forward and backward while potato leafhopper walks sideways as well as forward and backward.
White apple leafhopper overwintering eggs begin hatching at pink, and hatching is usually complete by petal fall. The nymphs move to the undersides of the leaves to feed. First generation adults begin to appear in June. There are two generations of white apple leafhopper per year. The second-generation adults are often noticeable during harvest.
Monitor nymphs of white apple leafhopper from bloom through petal fall. If an average of 3 or more nymphs per leaf is detected, then use an insecticide specifically targeted for leafhopper, in addition to other insecticides that may be needed at petal fall. In orchards where leafhoppers have become troublesome, it is important to include an effective leafhopper control in the first cover spray. Young leafhoppers are easier to control than adults. The first brood is an easier target than the second brood because the hatch is more synchronous.
By Ric Bessin, Entomology Extension Specialist