Outbreaks of the variable oak leaf caterpillar may be severe but generally subside before serious tree mortality occurs. Parasites and predators are not effective in controlling rising populations of the insect. Mice and predaceous beetles feed on the resting larvae and pupae in the litter and soil of the forest floor. While no chemical is currently registered for control of this insect, chemical spraying has been effective and safe in controlling closely related insects.
LOCUST LEAFMINER, Xenochalepus dorsalis (Thunberg)
The locust leafminer is a destructive pest of black locust and honey locust in both the adult and larval stages. It is found throughout the range of these trees in the eastern half of North America. The adults also feed on other species of trees.
The adult beetles overwinter in crevices in the bark of trees and under litter on the forest floor. The beetles emerge and begin feeding in the spring, usually after mid-April. After feeding for a short time they deposit eggs on the undersides of leaves, piling them one upon another, somewhat shingle-like. Eggs are covered with brownish fecal matter. Larvae soon hatch and eat into the leaf tissue to form a mine. Newly emerged larvae feed gregariously in a single mine for a short time. They then construct new mines where the insects live singly. Several mines are constructed before the larvae reach maturity. The larvae pupate in the mines and emerge as adults in July to begin the second generation. The adult beetles are foliage feeders, eating irregular holes in leaves. When sufficient in number they may defoliate host trees.
Damage to black locust caused by the locust leaf miner.
Under forested conditions no control is recommended. Rarely do trees die from attacks by this insect. Damage is objectionable mostly from an aesthetic viewpoint.
COTTONWOOD LEAF BEETLE, Chrysomela scripta (F.)
Willows, poplars, aspens and alders are attacked by the cottonwood leaf beetle in the eastern United States. Cottonwood is the most important host in the South. Damage has been especially severe in Louisiana and Mississippi where thousands of acres of cottonwood plantations are intensively managed. Adult beetles and larvae feed on the foliage. Damage is most critical during the first three years after the cottonwood is planted. Adults chew holes in the leaves and may attack the terminal shoots causing reduced growth or stem deformity. Young larvae skeletonize the foliage but older larvae consume all foliage except the leaf midribs. Damage may become severe enough to cause mortality.
