Insect Pests We’re Noticing Now – Cankerworms

If you’ve been outside in the past week or so, you’ve probably noticed little green inchworms. While my 9 year old daughter thinks they’re adorable, they are actually pests called cankerworms. Two species, spring and fall cankerworms, hatch in early spring. The larvae (those inchworms we’re seeing) feed on young leaves before dropping to the ground on a silk thread. The larvae then pupate in leaf litter through the summer. When the adults emerge, the females climb trees and deposit eggs on twigs. Fall cankerworm adults climb in October – November, while spring cankerworm adults emerge in early spring.

While these cankerworms will generally not kill a tree, they can defoliate enough branches to cause the tree to be unsightly, and could potentially weaken trees.

While control of these pests would be difficult and costly at this time of year, banding your trees and applying a sticky substance called Tanglefoot (TM) in the fall can trap the adult females and prevent them from laying eggs. This video from NCSU shows how to apply the bands to a tree. Workshops have been held in Durham during previous fall months, and will be publicized here when scheduled in the coming autumn.

2 thoughts on “Insect Pests We’re Noticing Now – Cankerworms

  1. SCB

    I have a question. In the morning I will use a long bamboo pole to knock some of the worms off my trees. The ground will be littered with them. They will then try to climb back up the tree trunk but will get stuck in the Tanglefoot. Is there any real value to this practice? My neighbors think this a lost cause but my thought is that every worm I see stuck in Tanglefoot is one more leaf on my tree! Am I wasting my time/

    1. Since the cankerworm larvae finish feeding and drop to the ground by late April – early May, trees will have plenty of time to recover and refoliate if a large population of cankerworms have been feeding. The Tanglefoot (assuming you reapply in the fall) will trap the adult females before they lay next season’s eggs. I’m not sure that knocking the larvae from the tree now will make a significant difference in either the current season’s damage or in next year’s population, but go ahead if you really can’t stand seeing them in your trees.

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