DR. McKAY: I'd like to ask what effect low temperature has on them and how far north you think will be their limit?
DR. ADAMS: The soil temperature at which the grubs begin to die in hibernation is 15 degrees, and I have never seen the soil temperature that low here under turf. (I operate a soil thermograph on my lawn.)
A MEMBER: How far down do they go?
DR. ADAMS: They hibernate at 4 to 8 inches in the ground. It's rare to have it drop below 27 degrees at these depths.
MR. STERLING SMITH: What do you mean, Fahrenheit?
DR. ADAMS: That is Fahrenheit.
A MEMBER: That's frozen solid. That's at 32 degrees.
DR. ADAMS: The deeper soil will drop only a few degrees below freezing. The soil here usually remains no lower than 32 degrees, except within an inch or two of the top.
A MEMBER: Do you think soil temperature is going to be a limiting factor?
DR. ADAMS: I think the limiting factor northward is the coolness of the summers. In Northern Japan their life history gets altered because of the shortness of the summer, and I think in the Adirondack area they won't be serious for that reason.