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Caliroa cerasi (Linnaeus) (Hymenoptera: Tenthredinidae)
HostsPear sawfly prefers pears and cherries but will also damage leaves of plum, quince, and occasionally apple. Eggs are often laid on peach leaves in trees near infested pear and cherry orchards, but larvae do not thrive on peach.
Egg: The egg is small, white and oval, and looks like a small blister on the leaf. Eggs are laid just under the upper epidermis, the leaf's topmost layer of cells. Larva: The larva passes through five instars. The young larva resembles a small slug due to the olive green slime that covers its body. The front end of the insect is wider than the rest of the body. The back end is slightly tapered and raised a little from the leaf surface on which it feeds. Newly molted larvae are yellow until the slime is secreted. During the last instar, the larva loses its slimy covering and is a light orange-yellow color. At this stage, it is about 3/8 inch (10 mm) long and has 10 pairs of legs. Adult: The adult is a glossy black wasp, about 1/5 inch (5 mm) long.
Pear slug larva and foliar feeding damage (E. Beers, 28 September 2001)
Life historyPear sawfly overwinters as a pupa in a cocoon 2 to 3 inches deep in the soil. In the Northwest, first-generation adults emerge over an extended period in late spring. The adult female inserts eggs into the leaf tissue with her saw-like ovipositor. Incubation lasts 10 to 15 days. Larvae are present in late spring or early summer and immediately begin to feed on the upper surface of the leaf. It takes 3 to 4 weeks for the larvae to pass through the five stages of development. Fifth instar larvae do not feed but crawl or drop to the ground and pupate.
Second generation adults begin to emerge in July. They emerge over a shorter period of time than the first generation. Adults lay eggs soon after mating, and larvae appear in August and September. It is this generation of larvae that is the most destructive. Mature larvae drop to the ground for the overwintering pupal stage.