|University of Kentucky Entomology|
by Lee Townsend, Extension Entomologist
University of Kentucky Department of Entomology
Paleacrita vernata (Spring cankerworm)
Alsophila pometaria (Fall cankerworm) pdf version
Cankerworms are present every year, usually the damage goes unnoticed and healthy trees are not harmed by light feeding. However, damaging outbreaks occasionally occur and can continue for two to three seasons. Feeding begins in early spring as leaves start to expand and continues for three to four weeks. These caterpillars eat elm, apple, oak, and many fruit and shade trees, consuming entire leaves and leaving only the large veins. The greatest feeding occurs about the time the leaves become fully developed. Trees may be completely stripped of leaves during outbreak years and may be stressed or weakened as they use reserves to refoliate. Full grown cankerworks either crawl or drop to the ground on silken threads and pupate in the soil. There is one generation each year.
Generally, is is not practical to control cankerworms in forests and woodlots but homeowners may choose to protect landscape trees from defloiation. If an outbreak can be anticipated, tanglefoot applied to tree trunks in a band two to four feet aboveground will prevent female moths from crawling up and laying eggs in the trees. This technique may be preferred to insecticide sprays, especially when dealing with very large trees. Insecticides labeled for caterpillar control on shade trees should be applied before most larvae are more than one inch long.
CAUTION! Pesticide recommendations in this publication are registered for use in Kentucky, USA ONLY! The use of some products may not be legal in your state or country. Please check with your local county agent or regulatory official before using any pesticide mentioned in this publication.
Of course, ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY PESTICIDE!
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