Southeastern Apple Production
ENTOMOLOGY
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Southeastern Apple ProductionENTOMOLOGY |
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Young white apple leafhoppers (WALH) are tiny, whitish green, wingless, and are usually found on the underside of older leaves. They move forward and backward quickly (potato leafhoppers may move sideways as well). Adults are greenish white, 1/3 inch long, and appear wedge-shaped from above. They fly readily when disturbed. Eggs are about 1/25 inch long, creamy-white, and cylindrical.
Adult |
Nymphs |
 Nymph detail |
WALH overwinter as eggs in the bark of 1- to 5-year-old wood. Eggs begin hatching at pink, and adults develop in June. They are active for several weeks, during which time they lay eggs in the petioles and veins of leaves. The eggs begin to hatch during June. WALH feed in the orchard until autumn and lay overwintering eggs in young wood during September and early October.
WALH are leaf feeders and do not directly attack fruit. As sap is sucked from the leaves, green tissue is destroyed, causing leaves to become speckled or mottled with white spots. Besides injuring leaves, leafhoppers deposit numerous small spots of excrement on fruit, potentially reducing its quality.
 Speckled leaves |
Growers should monitor for WALH nymphs starting at petal fall. Young WALH are much easier to control than adults, and effective control of the first brood may prevent high populations of the second. The first brood is also a better target since the hatch is fairly synchronous and leafhoppers at this age are vulnerable to insecticides. Use of the insecticide carbaryl as an apple thinner often provides excellent control of this pest.
To monitor, count the total number of nymphs on the underside of 10 leaves on each of 10 sample trees. For
first generation nymphs, sample from petal fall to second cover. Timing of the
second generation varies, ranging from mid to late July in North Carolina to
early July in Georgia. Insecticide should be sprayed for the first generation
when populations reach an average of 1/4 nymph per leaf, and for the second
generation if populations reach 1 nymph per leaf. (Controlling the first generation
usually eliminates the need to control the second.)
Since WALH control generally requires use of carbamate insecticides, and since carbamates are detrimental to mite predators, controlling WALH can lead to mite outbreaks. If control is necessary, try to treat early in the season before mite predator numbers build up. Thorough coverage of upper and lower leaf surfaces is necessary for effective control.
Insect and Mite Management Overview
Insect and Mite Index
Southeastern Apple Production
Mountain
Horticultural Crops Research & Extension
Center
455 Research Drive
Mills River, NC 28759
Phone: 828.684.3562 ~ Fax: 828.684.8715
Email: jim_walgenbach@ncsu.edu
Web Crafters: Anne S. Napier and
Steve Schoof
Email:
steve_schoof@ncsu.edu
Updated March 13, 2007