On Jan 27, 2008, Malus2006 from Coon Rapids, MN (Zone 4a) wrote:
This nonnative pest eats trees of the genus Pinus. They prefer Mugo, Scotch, Red, and Jack Pine. They are not often listed in many common books. Their larvaes are the most destructive form. From observation on my Red Pine trees, the caterpillar- like larvae feed enmass on older needles, never feeding on new needles, leaving branches bare with only fresh needles on the edge, giving the tree an ugly appearance. They are easily noticed because there are many to each branch. They also leaves a good amount of dropping beneath each tree - the dropping is green and look like very tiny rabbit pellets. The larvaes feed late April to May or June.
In another area I have seen them feeding on Mugo Pines too.
Neodiprion feeds on Ponderosa pines in Central Wyoming. At rest, clumps of larvae mimic bunched pine needles, holding themselves very still unless disturbed. I have not witnessed birds feeding on the larvae. Kill the larvae with any product containg neem, or you can also try insecticidal soap, which I have found only marginally effective. Control eggs in needle litter beneath pine trees by raking up and burning the needles.