Scallop Shell moth

The Scallop Shell moth (Calocalpe undulata) is a member of the order Lepidoptera and the family Geometridae. This moth is primarily found in woodland environments and landscaped areas where its larvae can occasionally reach population densities that pose a threat to specific deciduous trees and shrubs.

This pest mainly targets species within the Salix (willow) genus, as well as blueberry, aspen, alder, and bird cherry. The larvae are known for their habit of spinning leaves together with silk threads to create protective webbed shelters, which allow them to feed undisturbed while remaining hidden from predators.

The species completes one generation per year. It typically overwinters in the pupal stage, nestled within the leaf litter or the top layer of soil surrounding the host plant. Adult moths emerge in early summer, and after mating, females deposit their eggs on the undersides of leaves. The larvae emerge shortly after and feed continuously throughout the summer months.

The damage caused by the larvae manifests as skeletonization or complete consumption of the leaf tissue. When infestations are severe, significant defoliation occurs, which weakens the host tree's overall vigor. This makes the affected plants more susceptible to secondary stressors, including drought, fungal diseases, and other pest infestations.

To effectively manage populations of the Scallop Shell moth, integrated pest management strategies are recommended:

• manual removal and disposal of webbed leaf clusters containing larvae;
• cultivation or soil disturbance under tree canopies to destroy pupae overwintering in the ground;
• application of appropriate insecticides during the early larval development stage;
• promoting a healthy environment for natural predators, such as birds and parasitic wasps, which can help keep the population in check.