Biology of Gypsonoma haimbachiana (Lepidoptera: Olethreutidae), a Twig Borer in Eastern Cottonwood

Gypsonoma haimbachiana (Kearfott) causes serious stunting, forking, and other malformations in cottonwood, particularly the young trees. There are 5 larval instars. A summer generation develops in 40–45 days, and there is evidence of 4 or 5 generations per year. The insects overwinter as larvae in shelters on the twigs or in terminal buds. The eggs are laid near a vein on the leaf and the larvae feed in the leaf tissues until their first molt. They then tunnel into new shoots to complete their larval development. They pupate in thin cocoons in bark crevices or in sheltered areas on the ground.