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Importance - The cottonwood twig borer is widely distributed throughout the eastern United States, from Canada to the Gulf states and west to Missouri. It is one of the most destructive insects of young cottonwood. Other poplars are also hosts. Terminal shoot injuries cause serious stunting, forks, crooks, and other malformations. This leads to reduction in the quality and quantity of merchantable pulpwood, sawlogs, or veneer.
Identifying the Insect - The adult is ash gray and has wingspread of 1/2 to 7/10 inch (13 to 17 mm). The basal portion of the forewing is darker than the apical. Fullgrown larvae are pale, with a brown-yellow head. They are from 2/5 to 1/2 inch (10 to 13 mm long).
Identifying the Injury - Larvae bore into the terminals and branch ends of the host. They frequently kill the bud and up to 10 inches (25 cm) of the terminal. Often the old dead terminal remains intact on the tree for several months after the larvae have emerged. A stunted, deformed, limby tree is a good indication of cottonwood twig borer damage.
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Potter wasp predator digging out cottonwood twig borer.
Photo by R.C. Morris, USDA Forest Service |
