Question
I live in a rural area in southern Indiana near the Ohio River and have numerous small pines on my property. I believe these are white pines.  They seem to self =propagate and have always seemed quite healthy.  Today I noticed that a group of three to six foot tall pines had large areas of missing needles as if they had been eaten off down to the branch.  I found swarms of yellow caterpillars with black markings on the branches.  I sprayed them with Bt and hope this will kill them before they do any more damage.  My question is what are these things?  Why have I never seen them before?  Are there likely to be more that will devastate my pines?  (Many of them are much too tall to spray.)  Is there any thing else I can do to eradicate them? Help!

Answer
Sounds like the "caterpillars" you discribed are Sawflies. I base this on the fact that the only "caterpillar" type insect that defoliates pines is sawflies. Exactly which sawfly you have would be difficult to determine without looking at the insect. What you are seeing is the larva stage of the sawfly. Bt is one of the controls so this should kill them. Sawflies have usually only one or maybe two (further South)life cycles per year. Normally their population does not increase much (usually natural predators keep them in check). If you want to determine which sawfly you have or confirm this or talk to someone local I would contact the Forest Health Specialist with the Indiana State Forestry agency. His name is Phil Marshall, pmarshall.dnr.state.in.us
Phone nimber 812-358-3621. Phil is a fellow Forest Health Specialist, you can mention my name as a reference. Good Luck!
Jim Hyland
Forest Health Specialist, Alabama