Birch sawfly (Arge pectoralis)
Dusky birch sawfly (Nematus latitarsus)
Pest description and damage Mature birch sawfly larvae are yellowish with rows of black spots along the abdomen and 0.75 inch in length. The head is reddish yellow with black eyespots. Adults are about 0.3 inch long, have 3-segmented antennae and lay eggs in rows on the edges of leaves. Larvae feed on birch, alder, and willow. Usually, damage is localized and rarely does larval feeding cause significant defoliation. Mature larvae of the dusky birch sawfly are about 0.5 inch in length, darker yellowish green, with three dark spots on each segment. They also feed on birch, but usually cause only localized damage. Larvae feed gregariously along the leaf edge holding with their abdomen flipped upside down over their back. Adults are 0.5 inch in length and resemble small wasps. There are two generations of dusky birch sawfly: spring and fall. However, they overwinter in the soil as pupae with adults emerging in spring.
Management-cultural control
Watch for small larvae along the leaf edge in spring. Prune out leaf or area with larvae.
Management-biological control
Stink bugs and other predator bugs have been known to prey upon the larvae.
Management-chemical control
See Table 2 in:
Chemical Control of Landscape Pests
For more information
See "Sawfly" in:
Furniss, R.L. and V.M. Carolyn. 1980. Western Forest Insects. USDA Forest Service, Misc. Pub 1339.