Tents of webbing on the tree - The leaves look browned, scorched. Sometimes individual worms can be seen hanging from a branch on a thread of silk.
Mimosa Webworm - This pest is the most serious problem of Honeylocusts, especially the thornless ones. Most common in the Midwest, these pests are expected to eventually spread wherever Honeylocusts are grown. The adult moth is silvery gray, with black dots all over its wings. It overwinters in the bark on the trunk of the Honeylocust or in debris under the tree. It emerges in June to lay its eggs on its leaves. Its larvae, or worms, have five white stripes running along their gray or brown bodies. When they hatch, they web leaves together to form a protective tent, under which they feed on the rest of the leaves. In southern regions webworms may produce several broods in one year . Sunburst with its golden foliage is highly susceptible to attack, Moraine and Shademaster less so.
Leaves Consumed - Tawny egg masses may be visible later in the season.
Gypsy moth caterpillar - Newly hatched gypsy moth caterpillars are about 1/16 inch long, and grow to about 2 1/2 inches. Mature ones have 5 pairs of blue spots and 6 pairs of red spots along their backs. Adult male moths have a wingspan of 1 1/2 inches, are light tan to dark brown, with blackish wavy bands across the forewings. Female moths are larger, nearly white. They have 2 1/2 inch wings but do not fly. Their egg masses are covered with velvety, buff-colored hairs, and contain 400 to 500 eggs. When they hatch, the caterpillars of the gypsy moth gather in huge masses to devour tree foliage. For more information see the file on Controlling Gypsy Moth
Globular Galls at growing tips
Gall Midge - A tiny pest (called a Gall Midge) rasps the insides of leaves which causes a gall about 1/8 inch in diameter to form where tissues are irritated. Midge larvae live within these galls at the ends of new growth on Honeylocust trees. The first eggs are laid in April and may be followed by 5 or more midge broods over the season.
Small bumps on leaves and twigs - The first indication a scale attack is often discoloration of the upper leaf surface, followed by leaf drop, reduced growth, and stunted plants.
Scale insects - Scale insects form clusters of circular gray bumps about 1/10 inch in diameter on Honeylocusts. These blister-like outgrowths have a distinctive raised nipple in the center and shield the insect while it feeds on the tree leaves and stems beneath. Heavy infestations kill young trees. For more information see the file on Controlling Scale
Cankers on trunk and branches, wilting and dieback - Affected trees develop cankers, or sores, on their trunks and branches. The cankers are elongated, sometimes sunken in the middle when new, and they often eventually girdle the tree. Commonly the bark turns orangish-brown or pale yellow orange and, in the South, a gummy substance leaks from the damaged tissue.
Canker disease - While relatively disease free in the wild, in their natural habitat, cultivated Honeylocusts are sometimes victims of a canker disease caused by a fungus. It has been linked to drought stress, occurring as it does, most frequently in the Great Plains region. There is some suspicion that cankers may also be caused by pruning wounds or sunburn. For more information see the file on Controlling Fungal Disease