Dogwood Sawfly Fact Sheet
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Dogwood Sawfly, Macremphytus tarsatus, is a significant pest to dogwood (Cornus) species. Because the Dogwood Sawfly takes on several forms while in the larval stage, it may not be easy to identify. Even the first instars can devour small portions of leaves, with groups of them producing a skeletonized appearance to the leaves. However, the larger final instar can consume entire leaves, leaving only the tougher leaf midribs.
|Dogwood sawfly larva
||Dogwood sawfly larvae coverd with white powdery
material feeding on the foliage of Cornus sericia
Dogwood sawfly’s host plants are dogwoods (Cornus species), particularly Cornus racemosa, gray dogwood and, just slightly less so, Cornus sericea, the osier dogwood. The larval stages can cause extensive leaf damage over the course of the summer, but there is little risk of plant mortality since defoliation is accomplished late in the growing season.
|Feeding damage from Dogwood sawfly larva on
The wasp-like adult sawfly lays eggs that hatch into larvae, the first instar of which is an almost translucent yellow. Look for groups of these larvae on the undersides of leaves that are being skeletonized. The second instar appears to be covered with a chalky powder, and the last instar is a one inch long creamy-yellow larva that has a shiny black head and black spots.
||Grown larvae overwinter in rotting wood on the ground. They may over-winter in wooden structures, where woodpeckers may seek them and damage the structures in the process.
||Adult sawflies emerge in late spring or early summer (May through July). Females lay their eggs on the undersides of leaves. Recently hatched larvae appear a transparent yellow; however, the second molt leaves them covered with a white chalky substance.
||The last molt changes the larval appearance to yellow with a shiny black head and black spots, about one inch long. When these larva complete their growth, they no longer feed on the leaves, but instead focus on locating their
overwintering sites. There is one generation of Dogwood Sawfly per year in Pennsylvania.
Upon hatching the young larvae devour leaf portions, but as they enlarge, they consume even more of the leaves, leaving only midveins of the leaves. Overwintering in wooden structures may result in damage to those structures by woodpeckers searching for the grown larvae.
||Handpick and destroy the larva
||Occasionally parasitized by wasps
||Treat infested plants when larvae are active during late June through July. Chemical treatment after larvae reach one inch is ineffective, since larvae stop feeding and begin to prepare for overwintering. Horticultural oil, insecticidal soap as well as several traditional contact and systemic insecticides are registered for control in Pennsylvania.
Authored by: Susan Parker, Penn State Extension Project Associate
Edited by: Michael Masiuk, Extension Educator, Penn State University – Allegheny County
Images provided by Michael Masiuk
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