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.
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.
WALKINGSTICK, Diapheromera femorata (Say)
The walkingstick is a defoliator of broadleaved trees in North America. The black oaks, basswood, and wild cherry are the most common preferred hosts but numerous other hardwood species are attacked. This insect is widely distributed over the United States east of the Rocky Mountains as well as Manitoba and Ontario in Canada. At times, populations build in sufficient numbers to defoliate trees over large areas.
Male walkingsticks feeding on oak.
These slender, wingless, stick-like insects are pale green when young, but gradually change to a dark green, gray, or brown at maturity. The adult female measures up to three inches in length and is more stout-bodied than the male. Mating usually takes place in August and egg laying begins six to ten days later. The eggs are dropped to the ground where they overwinter in the leaf litter. In the northern part of the walkingstick’s range the eggs take two years to hatch. In the South, walkingstick eggs hatch the summer after they are laid, usually starting in mid-May. The newly hatched walkingstick looks like a miniature adult.