-- This pest skeletonizes leaves of red and white oaks. Repeated defoliations
retard growth, vigor, and mast crops, and kill some trees. It is also
called the slug oak sawfly because the larvae are covered with a coat
of slime that helps them ahdere to foliage.
Insect (figure 8a). -- Larvae are slug-like, yellowish green and
shiny with a black head and legs, and .5 inch (12 mm) long. Larvae feed
in groups. The adult is a typical sawfly, about .25 inch (6-8 mm) long,
and light brown.
Injury (figure 8b). -- Leaves may be skeletonized. Larvae consume
the lower surface of the leaves, making the leaf transparent. Defoliation
starts in the upper crown in early summer and progresses downward. By
late summer, heavily infested trees may be completely defoliated.
-- Larvae in cocoons survive the winter. Larvae pupate in the spring.
Adults and larvae are present throughout the summer. Eggs are deposited
in single rows of slits on the lower leaf surface along main veins.
There are two to three generations per year.
-- Microbial diseases and other natural enemies generally keep the slug
oak sawfly in check. Insecticides may be needed on high value trees.
Figure 8. -- (a)
Slug oak sawfly larvae; (b) feeding injury by slug oak sawfly.