Sarrothripus Moth (Sarrothripus frigidana)

From: Ostry, Michael E.; Wilson, Louis F.; McNabb, Harold S., Jr.; Moore, Lincoln M. 1988. A guide to insect, disease, and animal pests of poplars. Agric. Handb. 677. Washington, DC: U.S. Department of Agriculture. 118 p.

Importance- Larvae consume leaves of young poplars and willows in nurseries and outplantings throughout North America. This insect's primary native host is balsam poplar, but it seldom seriously injures this species. Preferring 1- to 2-year-old trees, Sarrothripus may defoliate the upper crown of whips or young trees, causing growth loss and tip dieback. Look For: June-August Small yellow eggs in clusters of 2 to 5, near base of leaf petioles. July-September Leaves cupped and the openings covered with webbing, especially leaves in the upper crown or at ends of branches. Leaf surfaces skeletonized. Green or yellow larvae up to 1 inch long under the webbing.

Egg cluster of Sarrothripus moth.

Biology- This insect may have two generations each year. The female moth lays her eggs in small clusters at the base of leaves. When the larvae hatch, they migrate to the leaves and spin webs over the surface, making a tent in which they feed. Larvae move to new leaves after consuming the old ones. Mature larvae pupate in silken cocoons, either on the plant or in the soil beneath the crown. The insect is difficult to control with standard insecticides because the webbing reduces insecticide penetration.

Monitoring- Inspect whips of 1- to 2-year-old trees when leaves are nearly expanded. Examine 25 to 50 leaf clusters near the growing tips for eggs, webbing, or larvae. Treat nurseries if 20 percent of the whips are attacked. Treat plantings only if more than 50 percent of the trees are attacked or if dieback occurs in 20 percent or more of the trees.

Control: Apply a commercial preparation of Bt (Bacillus thuringiensis). Spray heavily infested trees with a systemic insecticide to control the larvae.

Sarrothripus larvae feeding on cupped leaf.