Fall webworm

The fall webworm (Hyphantria cunea) is a moth belonging to the family Erebidae. It is considered a significant invasive pest in many parts of the world, known for constructing distinctive silk webs over the foliage of its host plants, which serve as protection during its larval stages.

This species is highly polyphagous, feeding on hundreds of different plant species. Preferred hosts include fruit trees such as apple, cherry, and pear, as well as landscape trees like maple, willow, and walnut. Extensive feeding can lead to severe defoliation and long-term stress for the affected trees.

The biological cycle of the fall webworm generally includes two generations per year in temperate climates. Adults emerge in late spring or summer. Females lay large clusters of eggs on the underside of leaves. Once hatched, the larvae aggregate, weave silken nests, and feed gregariously, expanding the web as they consume more foliage.

The damage is primarily aesthetic and physiological. While a healthy, mature tree can usually withstand defoliation, repeated infestations over several years can kill younger trees or significantly reduce their vigor. The presence of the webs is the most reliable indicator of an infestation, making monitoring relatively straightforward.

Effective management strategies depend on early detection and the use of integrated pest management (IPM) practices:

• Pruning and destroying branches containing web nests before larvae disperse.
• Utilizing biological control agents such as Bacillus thuringiensis or natural predators.
• Implementing tree banding to capture migrating larvae or pupae.
• Applying systemic or contact insecticides when larvae are in early instars to ensure maximum efficiency.