Sap Feeders
Joseph Berger, Bugwood.org
L. Townsend, University of Kentucky
Boxelder bugs are black insects with red or orange markings that feed on sap in developing leaves or seeds; their feeding may result in discolored foliage. However, large numbers of boxelder bugs can develop and become accidental invaders as they move to shelter in cracks and crevices in the fall. They appear to be most abundant during hot, dry summers that follow warm springs.
James Solomon, USDA Forest Service, Bugwood.org
The boxelder twig borer, a small whitish-yellow caterpillar with a dark head, destroys the buds and tender shoots of boxelder and red maple. Feeding by this insect can cause trees to become bushy and lose their natural shape. By the time symptoms appear, the caterpillars have bored into the twig and are safe from any type of control measure. Any attempt to reduce damage to infested plants must be done before the small caterpillars have tunneled into the plant. Eggs hatch in mid-July and the small larvae feed for a short time on leaves. While feeding, they cover the area with silk which contains small waste pellets. For more information, see Entfact 415.
A. Steven Munson, USDA Forest Service, Bugwood.org
Fall cankerworm is a looper caterpillar that can vary from light green with yellow stripes to green with a dark stripe down the back. Overwintering masses of about 100 eggs hatch in later April or early May; small caterpillars chew small holes in young leaves at branch tips. Larger loopers leave only the midrib and major veins. Fall cankerworms are about an inch long when full grown. Mature larvae descend from trees on silk threads to pupate in the soil. They emerge as adults during periods of freezing temperatures to mate and lay eggs on host plants. There is one generation each year.
Also see Maple (Acer) as many of the same insects that feed on maples will also feed on boxelder.