https://phys.org/news/2018-06-pine-killing-southern-beetle-deadly-north.html

Now there's more bad news in a new study from Dartmouth College: Cooler fall and winter temperatures in this new range increase the beetle's destructive potential. That's because larvae developing in the fall are put on hold as pupae when the temperature drops below 50 degrees Fahrenheit (10 degrees Celsius), to emerge as adults for a mass killing spree in springtime.

The researchers found that in warmer regions, beetles mature at various times rather than all at once.