Cottonwood Twig Borer (Gypsonoma haimbachiana) - Larvae bore into newly developed shoots, killing shoots and causing irregular growth. Heavily injured trees become deformed, bushy, and of little value. This pest is found throughout eastern North America but is more serious in the South where there are multiple generations. This insect has from one generation in the North to five in the South. The adult moths emerge from cocoons in spring; soon after the females lay eggs singly or in small clusters on the upper leaf surface. Young larvae feed on the leaves and veins until they molt, then they move to the base of developing leaves and tunnel into the tender shoots. Full-grown larvae move down the tree and spin cocoons in bark crevices or in the litter under the trees. In warmer areas the borer produces more generations, and larvae of the last generation overwinter in small silken shelters on the shoots. These larvae move to new shoots in spring and complete their growth.