Possible Cankerworms on Mature Trees

Asked May 1, 2013, 2:48 PM EDT

The Trinity Church/Old Sycamore Rd. area of Charles county is having an "epidemic" of what we believe are cankerworms (inchworms that drop from the trees on webs). Some are green, others have black lines. They are doing considerable damage to oak and beech trees - almost defoliating some. These are well established 50" + trees. They are also eating some azaleas and crepe myrtles. They are all over the house and outbuildings. You can't walk outside without getting full of worms. How long will this last and what can be done? Am concerned about old, mature trees.

Charles County Maryland trees and shrubs insects cankerworms horticulture

1 Response

There have been numerous reports of cankerworms feeding on mature oak and beech trees in your area. There are two species of these insects active right now, the spring cankerworm and (ironically) the fall cankerworm. They will feed together on the same tree. Their activity will end in mid- to late-May. If a tree suffers serious defoliation in two successive years, the damage could be lethal, so it is recommended that you hire a certified arborist to spray the tree(s) with an appropriate insecticide.. They will have adequate equipment and access to chemical products that are effective, but the treatment must be done while the caterpillars are active. It is possible for homeowners to spray smaller plants, such as azaleas and crape myrtles with an across-the-counter product containing Bacillus thurengiensis, Bt.