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.
[Illustration: Cottonwood leaf beetle adult.]
The cottonwood leaf beetle overwinters in the adult stage. Eggs are laid
in the spring. The female lays a cluster of about 75 yellowish eggs on
the underside of a leaf. As the larvae mature they become yellow with
black spots. After about nine days in the larval stage the beetle
transforms into the non-feeding pupal stage which lasts five to ten
days. The adult is about ¼-inch long and has a black head and thorax.
The wing covers are yellow with longitudinal black stripes. The life
cycle is completed in 25 to 30 days and several generations occur in a
single year.
[Illustration: Larvae and pupae of the cottonwood leaf beetle.]
Control may be needed in a plantation only during the first three years.
Chemical sprays have been successful in the past but at the present time
no insecticides are registered for cottonwood leaf beetle control.