This oak leaf tier has been associated with the decline and mortality of
several species of oak in the northeastern United States and southern
Appalachians. An outbreak population in the mountains of West Virginia
and Virginia in 1966-68 resulted in the loss of several thousand acres
of scarlet oak. Usually such outbreaks coincide with periods of drought
which increase the impact of defoliation on the host. Its hosts include
northern red oak, black oak, scarlet oak, and pin oak. The latter two
species seem to be hit hardest by this insect.
[Illustration: 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.
[Illustration: 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.