Will this extreme cold kill off the Japanese Beetles?
Thank you for the question. We're not sure if the cold will contribute to a reduced population of Japanese beetles this summer because the grubs burrow deeper in the soil as it gets colder in an effort to protect themselves. We do know that dry soil conditions can result in fewer viable eggs and reduced adult populations.
These publications might be of interest to you even though they're not specific to Ramsey County. I'm not sure which winter's they reference, but I don't think it's this one:
Thank you for contacting Extension.