-- This defoliator is common throughout eastern North America. It feeds
on all species of oaks, but prefers the white oaks. Some infestations
have covered millions of acres - retarding growth and tree vigor. Outbreaks
usually subside after 2 to 3 years, before serious tree mortality occurs.
Insect (figure 4a). -- Caterpillar coloration is variable, but is
generally yellowish green with a narrow white stripe down the center
of the back, bordered dorsally with reddish-brown, and one or two yellowish
stripes on the sides. Mature larvae may reach 1.5 inches (37 mm) long.
The adult moth is ashy grey with three dark wavy lines across the forewings.
Injury (figure 4b). -- Young larvae skeletonize the leaf while older
larvae devour the entire leaf except the leaf stalks and main veins.
There are two periods of defoliation - one in June to July and another
in August to October.
-- There are two generations in the South and one generation in the
North. In the South, the larvae feed from early May until late June,
and pupate in the soil. Second-generation larvae feed from mid-August
until late September, then move to the ground to spin cocoons and overwinter
as prepupae. Larvae of the single generation in the North are present
during June to midAugust.
-- Insect parasites and predators eat the eggs and larvae of this pest.
Winter mortality also helps keep most infestations in check. Chemical
control is occasionally needed to protect high-value trees.
Figure 4. (a) Variable
oakleaf caterpillar larva; (b) defoliation by variable oakleaf caterpillar
in residential area.