Insects and Diseases of Trees in the South

by Anonymous

Leaf tier adult and pupa.

Croesia albicomana spends the winter in the egg stage. Eggs are glued to small twigs in the crown of the host tree. Hatch occurs from mid-April to early May. Young larvae, which emerge before bud-break, bore into and mine the expanding buds. When large numbers of this insect are present they can destroy most of the vegetative buds on a tree. Later the older larvae tie down a folded-over portion of a leaf and feed on it. Leaves fed on by the oak leaf tier appear to be full of shot holes. As the larvae near maturity they may tie the apical portion of two or more leaves together and feed on them. Mature larvae then drop to the ground to pupate in the litter. Adult moths emerge in June or early July, mate, and the female immediately begins laying eggs. The small, flat, oval eggs are deposited individually on small twigs, generally around nodes or leaf scars.

Scarlet oak killed by leaf tier.

Little is known of the natural factors which regulate population levels of this insect, but undoubtedly weather is important.

VARIABLE OAK LEAF CATERPILLAR, Heterocampa maneto (Dbldy.)

The variable oak leaf caterpillar periodically defoliates extensive areas of hardwood forest in the eastern United States. Its range covers all of the southern and eastern states as far west as east Texas. The larvae feed primarily on oaks but will also feed on beech, basswood, birch and elm. Other defoliating insects may be associated with outbreaks causing additional damage. Young larvae skeletonize the leaf while older larvae devour the entire leaf except the primary veins. Infestations are generally more severe in the South, where the insect has two generations per year causing two periods of defoliation in a single year. While infestations usually subside before many trees are killed, heavy defoliation reduces the tree’s growth and vigor.

Larva of the variable oak leaf caterpillar.

The variable oak leaf caterpillar overwinters as a non-feeding larva in a cocoon on the forest floor. It pupates and emerges as a moth the following spring. The female moth, gray in color and about 1¾ inches long, lays about 500 eggs singly on the leaves of host trees. The larvae feed on foliage for five or six weeks, drop to the ground to pupate, and emerge as adults in mid-summer. Larvae hatching from eggs laid by the second generation of moths defoliate the trees for a second time during late summer. By late October the mature larvae of the second generation have dropped to the forest floor to overwinter. The full grown larva is approximately 1½ inches long. Color varies among individuals. The head is generally amber brown with curved diagonal white and black bands. The body is usually yellow green with a narrow white stripe down the center of the back bordered by wider dark bands.