To my limited experience pines are very sensitive to piercings, ie. fencing, ropes, nails and so on. Is it possible this was because of a fence-line or something similar? I don't know about redrot and am not an arborist (learning curve) but the last dead one I cut had black stain for at least three feet on either side of where there was wire. Like I said, I know nothing but am curious as we have many pines here in the NW coast and I find many dead ones that usually aren't much more than 20-35 years old, and yes, these are ones near properties and ones to be very wary of (wire does wonders for chains as most of you know).