Leaf Feeders
Hackberry caterpillars are yellow to light green with a pair of white or yellow lines that that run from head to tail. There are slanted light marks along the sides. This distinctive caterpillar has two barbed horns behind the head and a pair of pointed projections from the rear of the body. There are 2 generations each year and occasionally they may be abundant enough to cause significant defoliation.
Sap Feeders
Raymond Gill, California Department of Food and Agriculture, Bugwood.org
Calico scale is a white and dark brown soft scale about 1/4 inch in diameter. It produces a large amount of honeydew in the spring so twigs, branches, and leaves may be covered with sooty mold. This scale can severely weaken trees, making them more vulnerable to drought and other stresses. Egg hatch occurs in May and the crawlers move to leaves to feed for the summer. Nymphs move back to bark for the winter.
Whitney Cranshaw, Colorado State University, Bugwood.org
Hackberry lace bugs are 1/8 to 3/16 inches long sap-feeding insects with clear, ornate, lacy wings; nymphs are spiny and wingless. Both stages live on the lower surface of leaves. As they feed, they leave tiny yellow to white spots on leaves and dark, varnish-like waste spots on the under sides.
These lace bugs spend the winter as eggs under bark or in leaf litter. The eggs hatch in early spring and the nymphs begin to feed on plant sap. There are several generations each season. Initially, numbers are so small that feeding symptoms are not noticed until the population peaks in late summer. When abundant, feeding can make plants unsightly and may cause premature leaf drop.
Asian wooly hackberry aphids look similar to other aphids, except they also have a wooly coating much like a mealy bug. Winged forms may also be observed and wings have obvious black markings on them. They feed on sap and produce large amounts of honeydew, which can in turn cause problems with black sooty mold growth. They overwinter as eggs on the tree and emerge in the spring with new leaf growth. During spring and summer the females will reproduce asexually.
Sturgis McKeever, Georgia Southern University, Bugwood.org
Cottony cushion scale is an invasive scale species that can be found feeding on the sap of numerous species of plants. Adult females are orange-brown but coated with white wax and will have a long, fluted egg sac attached to the body. This can contain up to 1,000 eggs. After hatching, the nymphs (which are red with dark antennae and legs) will seek a suitable space for feeding. Nymphal feeding on leaves can cause extensive damage and honeydew/black sooty mold will accumulate as the population builds.
Borers
Petr Kapitola, Central Institute for Supervising and Testing in Agriculture,
Bugwood.org (larva);James Solomon, USDA Forest Service, Bugwood.org (adult)
Both the caterpillar and adult of the Wood leopard moth are very distinctive. The caterpillar is the damaging stage, feeding under the bark of host trees. It is a white-orange color with numerous spots on its body. The adult is white with six black dots on the thorax and black markings on the remainder of the body. Adults may be active June-September and larvae feed inside of plants for 2-3 years.
Galls
Steven Katovich, USDA Forest Service, Bugwood.org
Hackberry leaf galls are raised warts on leaves that are caused by small aphid-like insects that live within the growth. Heavily infested leaves may turn yellow and drop prematurely. This insect does not appear to affect tree health.