Integrated Pest Management - Growing development days (GDD) - Ask Extension
Hello, I am interested in knowing the growth development days (GDD) at the GDD 50 metric for sap beetles, which are responsible for spreading oak wilt...
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Integrated Pest Management - Growing development days (GDD) #928011
Asked April 10, 2026, 1:48 PM EDT
Hello, I am interested in knowing the growth development days (GDD) at the GDD 50 metric for sap beetles, which are responsible for spreading oak wilt. I do not see them listed on either of the pages below. Thank you!
https://www.canr.msu.edu/ipm/agriculture/christmas_trees/gdd_of_landscape_insects
https://www.canr.msu.edu/ipm/agriculture/christmas_trees/gdd_of_conifer_insects
Berrien County Michigan
Expert Response
I'm not aware of a growing degree day model for sap beetles. They can be active early in the season, and best practice is to avoid any pruning cuts April 15 - July 15. If any pruning needs to be done in the next few days, it would be advisable to treat and seal the wounds since we are so close to the main risk period of oak wilt infection.
David,
Thank you so much for the quick reply. There have been some isolated incidents of oak wilt in area (Sawyer, in Berrien County) over the last few years. Our arborist trimmed some deadwood out of a few oaks on our property 10 days ago, and they communicated we were still outside the high risk period at that point. Yet as I’m typically cautious about these things, I began to read about the GDD model and sap beetles to educate myself and feel a bit more confidence about their guidance.
Once again, I sincerely appreciate your response.
Best Regards,
Steve Nichols
On Apr 10, 2026, at 2:25 PM, Ask Extension wrote:
