Pest Identification

• The robust cottonwood borer (Plectrodera scalator) measures over 1 1/4 inches long; its body appears yellow, black and white with two long black antenna. Cottonwood borer larvae measure 1 1/2 inches in length and sport a brownish-black head. The cottonwood leaf beetle (Chrysomela scripta) has black speckling set against a reddish tan background. Each hard-bodied beetle measures 1/4 of an inch in length. Upon hatching, the cottonwood leaf beetle's larvae appear black but the color fades to brown, Quite noxious, the larvae secrete a smelly substance from body glands to repel potential predators. Adult poplar tent makers (Clostera inclusa) appear like ordinary brownish moths. The moth's caterpillars have a lightly furred body with shades of yellow and green. Upon maturity, the caterpillar measures just over 1 1/2 inches in length.
  
  

Damage

• The cottonwood tree borer lays its egg in pits it chews out near the tree's root system. The larvae burrow galleries into the tree's roots upon hatching. They take 3 to 5 years to reach maturity. The adults chew the tree's leaves and new growth. A young infested tree will die from girdling or become so severely weakened that it topples in a windstorm. The larvae of the cottonwood leaf beetle severely skeletonize the tree's leaves. The adult cottonwood leaf beetle enjoys feeding on the bark of cottonwood seedlings and can eventually kill the young tree. The larvae of the poplar tentmaker cause severe defoliation by skeletonizing and killing the tree's leaves.
  
  

Tree Care

• Maintaining the tree's overall health will help prevent it from perishing when infested with the cottonwood borer. The cottonwood leaf beetles pose a danger to trees younger than 3 years old. Older, well-maintained trees may experience some defoliation, but with proper care, the adult tree can tolerate the onslaught. Maintain a consistent irrigation and fertilizing plan to prevent the tree from suffering stress that can weaken it. Plant the cottonwood tree in a site with full or partial sunlight. It enjoys a site that has deep, moist soil. When planted in an acceptable location the cottonwood tree can live more than 100 years, according to the Great Plains Nature Center.
  
  

Control

• During the fall, dig up the larvae of the cottonwood borer around the tree's base and discard. Apply a permethrin-based spray in late June and early July to help prevent the adult cottonwood borers from laying eggs. Saturate the tree's base and trunk with the pesticide. Reapply it in late July. Apply insecticidal soaps and horticultural oils to help control the larvae of the cottonwood leaf beetle. Use an insecticide that contains chlorpyrifos, acephate, diazinon or carbaryl to control adult cottonwood leaf beetles. If the tree suffers from a light infestation of poplar tentmaker caterpillars, consider handpicking the insects to control them. Use insecticidal soaps on a moderate infestation. Conventional pesticides that contain acephate, diazinon or carbaryl can also control the caterpillars.