What Is Wrong With My Hickory Tree?

Are there any galls on leaves, stems, and twigs?

Are there holes in the bark, trunk, and branches are girdled?

Are there holes in the bark, twigs are wilted?

Are the leaves rolled together and discolored?

Are the trees defoliated?

Are the leaves browned or blotched?

Hickory leaf stem gall aphids are soft-bodied, pear-shaped sucking insects, about the size of the head of a pin. They cause hollow, green swollen growths (galls) to appear on leaves, stems, and new shoots in June. The galls are pea-sized to more than 1/2 inch in diameter. Control the aphids by spraying the trees with dormant oil in early spring to kill over-wintering insects.

Painted hickory borer grubs are creamy white, 3/4 inch long worms. They tunnel extensively beneath the bark, cutting off sap flow and girdling trunks and branches. Attracted to weakened trees, they lay their eggs in late May or early June. Larvae mature in 10 to 12 weeks, then pupate in the wood in September, where they remain until next spring. If the tunnels are fairly straight, kill the borer larva by probing the tunnel with a flexible wire.

Hickory bark beetle adults are dark brown, 1/5 inch long. The pests tunnel in the inner bark and sapwood and deposit eggs in small side-pockets. The hatching grubs tunnel away from the parent gallery and cut off sap flow as they feed, causing young twigs to wilt. Eventually, they may girdle the tree. The grubs overwinter under the bark. Adults emerge in June or July through holes resembling shot holes and eat the bases of the leaf stems, causing many leaves to turn brown in July. Infested trees should be cut and burned.

Hickory leafroller caterpillars are yellowish-green, about 1 inch long. Adult moths are dark brown with darker oblique bands on the forewings. These pests protect themselves while feeding by rolling terminal leaves into tubes and binding them with strands or webs of silk. Leaves are often skeletonized, turn brown and die. If the infestation isn't severe, handpick the rolled leaves with caterpillars. Spray more heavily infested trees with light horticultural oil according to the directions of the label to smother the insects and any eggs.

Gypsy moth caterpillars sometimes mass on hickory foliage and devour it, defoliating the tree. The tree may die after repeated defoliation. Mature caterpillars have 5 pairs of blue spots and 6 pairs of red spots along the back. In light infestations destroy eggs or pick caterpillars by hand, in more severe cases spray plants with BTK or pyrethrin as the last resort.

Anthracnose is a fungal disease that sometimes causes problems on hickory trees but it is not likely to kill the tree. Prune off affected parts and clean up and destroy fallen leaves in autumn. A dormant spray of lime-sulfur or Bordeaux mix may give some control.

Spotted leaves on hickory usually indicate fungal leaf spot. Some fungal spots are surrounded by flecks or black dots, their spore-bearing fruiting bodies. Often spots come together to form larger patches of dead tissue. Pick off and discard infected leaves. Remove dead leaves to reduce overwintering spore populations.