Pine root tip weevil, Hylobius rhizophagus, and pine root collar weevil, H. radicis, attack certain Scotch pine stands simultaneously causing more mortality than expected from either insect alone. Recommendations for curtailing this insect complex include favoring red pine, planting Scotch pine far from brood sources, and avoiding stump culture of Christmas trees.
Mosher, Daniel G. and Wilson, Louis F.
"Scotch Pine Deterioration in Michigan Caused by Pine Root Weevil Complex,"
The Great Lakes Entomologist, vol 10
Available at: https://scholar.valpo.edu/tgle/vol10/iss4/1