Prepare for Greenstripped Mapleworms
I got reports of rosy maple moths spotted around lights over the weekend. These beautiful moths are the adult form of greenstripped mapleworms which feed on maples each summer. They are many caterpillar pests of landscape and nursery trees.
The greenstriped mapleworm, Dryocampa rubicunda, is found throughout the Eastern United States and Canada. Maples are its preferred hosts and the most common hosts in many landscapes. In North Carolina, moths emerge from their pupae in late April or early May. The moths deposit yellow eggs on the underside of leaves.
The larvae have red or black heads, pale-green bodies with seven dark-green longitudinal stripes. There are two prominent horns on the second thoracic segment, two rows of short spines on the side of the body, and four larger spines on the terminal abdominal segments. Full-grown larvae can reach 40 mm in length.
Large populations of mapleworms can defoliate trees if unnoticed or without proper management. Rarely will the tree suffer long term damage but loss in growth and branch dieback may occur if the same tree is defoliated several consecutive years.
You can scout for eggs by examining the underside of leaves for egg masses and removing those leaves to reduce tree damage. Surveying tree canopies for leaf defoliation is one of the best ways to catch an infestation after egg hatch. Once they hatch larvae start feeding gregariously so you can find infested branches that have all the larvae from a single egg mass. Prune that branch and your pests are gone. Older larvae spread out to find more leaves but by that point you will notice obvious defoliation if many larvae are present. Also look for frass on the ground beneath trees.
Insecticides labeled for caterpillars are available in the Southeastern Pest Control Guide for Nursery Crops and Landscape Plantings.