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Oak Pests - A Guide to Major Insects, Diseases, Air Pollution and Chemical Injury


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FALL CANKERWORM
Alsophila pometaria

Importance. -- The fall cankerworm is one of the most common and injurious species of loopers in eastern forests. Repeated defoliation causes growth loss, reduction in mast, can eventually kill trees and causes a nuisance in high-use areas.

Identifying the Insect (figure 2a). -- Larval color varies with population density from light green with yellow stripes, to green with a dark dorsal stripe, to black with whitish lines. The mature larva is .8 to 1-inch (19 to 25 mm) long. The adult female is wingless and ash gray; males have wings. Eggs are laid in masses of more than 100 on small twigs (figure 2b).

Identifying the Injury (figure 2c). -- Early signs are small holes in leaves or complete skeletonization of the leaves. Larger larvae consume all except the midrib and major veins. Feeding is complete in 5 to 6 weeks.

Biology. -- Overwintering eggs hatch in late April or early May. The larvae feed on young leaves at branch tips. Mature larvae enter the soil to pupate. Adults emerge, mate, and deposit eggs in November and December. There is one generation per year.

Control. -- The eggs and larvae of the fall cankerworm are attacked by insect parasites. Other natural enemies also help control this pest. Sticky bands placed on trunks of high-value trees can snare the wingless females before they lay their eggs. Chemical controls may be needed.

Figure 2a
Figure 2b
Figure 2c

Figure 2. -- (a) Fall cankerworm larva; (b) fall cankerworm female moth and egg mass on branch; (c) oak stand defoliated by fall cankerworm.

 
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