Hi Peggy,

Thank you for contacting UNH Cooperative Extension with your concerns about the larvae that are attacking your dogwood.  Based on your photo, it appears the pest is the dogwood sawfly.  I have included links to fact sheets that discuss the various stages of the sawfly and how to manage them.  Also included below is information from the University of Maryland Extension about the dogwood sawfly.

If you would prefer an answer based on the identification of the larvae itself, I have included a link to the UNH Extension Insect Identification Service

https://extension.unh.edu/blog/2020/07/what-eating-my-dogwood-leaves

https://content.ces.ncsu.edu/dogwood-sawfly

https://hyg.ipm.illinois.edu/article.php?id=1243

https://extension.unh.edu/agriculture-gardens/pest-disease-growing-tools/insect-other-arthropods-identification

Dogwood Sawfly

• The dogwood sawfly is an occasional pest of dogwoods. They are mostly seen on shrub dogwoods - e.g., silky dogwood (Cornus amomum) and red osier dogwood (C. sericea).
• There is one generation each year. Monitor for them starting in early July.
• Upon hatching, the young larvae feed together and chew the leaves.
• After the second molt, the larvae become covered with a white powdery material.
• After their final molt, they lose the powdery covering and change color. The mature larvae are yellowish with a shiny black head and black spots.
• These mature larvae will wander about in search of an overwintering site, generally in soft or decaying wood.