Ailanthus webworm

The Ailanthus webworm (Atteva punctella) is a moth species belonging to the order Lepidoptera and the family Attevidae. It is primarily known as a specialized pest that targets the Tree of Heaven, Ailanthus altissima, although its range has expanded significantly in recent decades.

The host plant specificity is a defining biological trait of this insect. While the larvae feed almost exclusively on Ailanthus, the species is considered a pest in various urban and forest environments where the host tree is present. Its ability to exploit this fast-growing tree contributes to its status as a persistent nuisance.

The life cycle of the Ailanthus webworm involves four stages: egg, larva, pupa, and adult. The moths are known for their distinctively patterned wings. The larvae are gregarious, meaning they live and feed together in silken webs they construct on the foliage, which provides them with essential protection from birds and other predators.

Damage caused by this pest is characterized by the skeletalization of leaflets. As the larvae consume the leaf tissue within their webs, the foliage turns brown and appears withered. While healthy mature trees can often withstand defoliation, repeated attacks over multiple seasons can weaken the tree, especially in young saplings.

Integrated Pest Management (IPM) is the most effective approach to handle outbreaks. Recommendations include:

• Monitoring for web clusters during the growing season.
• Physical removal of infested branches if the tree size permits.
• Application of Bacillus thuringiensis (Bt) or appropriate insecticides when larvae are small and actively feeding.

Consistent observation is key, as the lifecycle can be rapid, allowing multiple generations to occur in a single summer. Proper identification and timely intervention ensure that the damage to decorative trees remains within manageable limits.