Issue 4, May 16, 2016

Grass Sawfly

Grass sawfly larvae have been found feeding on turf in northwestern Illinois. In the past, they have been found feeding on various species of Lysimachia, sometimes called loosestrife or creeping jenny. The sawfly larvae are whitish to pale green with light tan heads and obvious black eyes. Fully grown larvae are a little over one inch long. We're not sure which species this is, but it is likely Dolerus nitens as it is common as adults in late spring.

Glass sawfly larvae.

Grass sawfly larva on lysimachia firecracker.

These insects are unlikely to cause important damage to turf, but localized damage to Lysimachia may occur. It is likely that these insects are held in check by parasitic wasps, keeping them from being widespread pests. Although sawfly larvae look similar to caterpillars, they have more than five pairs of prolegs. Not being true caterpillars, they are not controlled with Btk. Spraying the foliage with carbaryl, Sevin, or a labeled pyrethroid will provide control. Do not spray blossoms to avoid killing bees and other pollinators. (Phil Nixon, Martha Smith)

Phil Nixon
Martha Smith

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