Issue 17, September 28, 2009

Dogwood Sawfly

There have been a few cases of dogwood sawfly reported recently. Dogwood sawfly feeds on the leaves of gray dogwood and other dogwood species from mid-summer to early fall. Although they can cause defoliation, they are not likely to cause serious harm to the health of the tree.

Dogwood sawfly overwinters as a larva in a cavity chewed out of rotting wood. It pupates and emerges as a wasp-like insect from May to July. This extended emergence period results in an extended feeding period. Eggs are laid on dogwood leaves. These eggs hatch into translucent yellowish larvae that eat the leaf lamina, leaving the veins intact.

Older larvae are covered with a white powder-like material that is easily rubbed off. They are obvious on the leaves, eating all of the leaf except the midvein. In their last molt, the larvae lose their white covering, being yellow with dark green backs. Fully grown larvae are about one inch long.

Being sawflies, the larvae have more than five pairs of prolegs and are not controlled with Bacillus thuringiensis kurstaki. Because the larvae are large and obvious, it is easy to hand-pick the larvae. A spray of carbaryl (Sevin) or a labeled pyrethroid such as cyfluthrin (Tempo, Bayer Multi-insect Killer) or permethrin (Astro, Eight Insect Spray) is also effective.--Phil Nixon

Phil Nixon

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