Galls On Leaves, Stems and Twigs
Gall Aphids - 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.
Holes In Bark, Trunk, Branches Girdled
Hickory Borers - Painted hickory borer grubs are creamy white, 3/4 inch long worms. They tunnel extensively beneath bark, cutting off sap flow and girdling trunks and branches. The adult beetles are dark brown, with zigzag lines on the back. 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.
Holes In Bark, Twigs Wilt
Hickory Bark Beetles - 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 over-winter 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.
Leaves Rolled Together, Discolored
Hickory Leaf rollers - 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.
Gypsy Moths - Gypsy moth caterpillars grow from about 1/16 inch long at hatching to about 2-1/2 inches long by the time they become pupae. Mature larvae are covered with black hairs and have 5 pairs of blue spots and 6 pairs of red spots along the back. In July, they encase themselves in brown shells to pupate. Trees infested with gypsy moths may be defoliated. Gypsy moth larvae are often confused with the eastern tent caterpillar and fall webworm, both of which make silken tents in trees. Gypsy moths do not make tents. Look for the distinctive tan egg masses on trunks and branches, under your roof eaves, and other protected spots. The eggs look like little gold pearls. Crush these or drop them into a pail of water mixed with kerosene.
Leaves Browned or Blotched. The trees may be defoliated in humid weather.
Anthracnose – This is a fungal disease. Collect fallen leaves to reduce populations of over-wintering disease spores. It is not likely to kill the tree.
Leaves Spotted or Blotched
Leaf Spot - Many kinds of leaf spots are caused by fungi that thrive on moist leaf surfaces and cause transparent to brown or black spots that disfigure the leaves. 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.