Oak leaf Rollers and Canker Worms

Defoliation of life oak trees by leaf-feeding worms will be here about the middle of March. While it has happened before, last year’s infestation taught us new lessons. More than one insect species was present. We had canker worms (inch worms) along with oak leaf rollers. Both species defoliate oak trees, drop from trees on silk threads and irritate homeowners.

Canker worms and leaf rollers have different developmental characteristics. Spring Canker worm larvae consume foliage, drop to the soil on silk threads, go into the resting stage (pupate) and then develop into adult wingless moths. They climb host trees and lay eggs in March and April. Eggs hatch the next March and April, larvae develop and a new round of destruction begins. Last fall we had a deluge of moths, the male moth is winged.

Maturing leaf roller larvae also drop to the ground on silk threads and enter the pupal stage. Their pupae soon develop into winged moths. About the first of May these adults fly to oak trees and begin laying eggs. Deposited eggs remain dormant for 10 months and start hatching the following February and March. Then, their destructive cycle begins.

It makes little difference to homeowners whether these voracious worms are canker worms or leaf rollers. They occur at the same time and cause the same type of damage. They’re about the same size, strip trees of foliage and drop to the ground on silk threads. Individuals who want to know the difference can observe crawling worms. If they walk with humps in their backs they’re inchworms, or canker worms. If they wiggle vigorously in an effort to escape, they’re oak leaf rollers.

Canker worms and oak leaf rollers each produce only one generation per year. Once eggs hatch and larvae mature, the event is over for the year. If the trees are sprayed when the spring leaves emerge the caterpillars can be killed. The destructive period may last from three to five weeks, depending on several factors. An insect growth regulator sprayed on the tree and the debris on the ground will kill the caterpillars. Breaking the life cycle will reduce the number of caterpillars.

Don’t get the idea that devastating infestations occur every year. They don’t. While some worms develop each year, light infestations usually go unnoticed. Predatory insects and diseases serve to keep populations in check. Predicting future infestations is difficult, if not impossible.

The two species of worms mentioned here are incapable of causing physical harm to people. This doesn’t rule out the possibility that people may discover worms in their hair or on clothing and injure themselves, however.