Hello, 

Thanks for reaching out! Here is an article with more information about the European Pine Sawfly (scroll down to the "Sawflies on Coniferous Trees and Shrubs" section): https://extension.umn.edu/yard-and-garden-insects/sawflies

Recommended management is: 

1. Spot treat when possible as European pine sawflies commonly feed in groups

2. In the fall, apply imidacloprid or dinotefuron to the soil to control larvae for the following spring

3. In the spring, apply a pesticide when you see larvae in the branches. Look for a pesticide that lists sawflies on the label. 

Always read pesticide labels prior to use. Follow the label directions attached to the pesticide container you are using. Remember, the label is the law.

Good luck!