Wayne,
Is there any chance that you have any of the following situations:
1) Walnut trees growing near your pines? Or hickory or pecan? Any nuts trees nearby?
2) Compost used near your pines and possibly containing walnut components?
3) Mulch which could contain walnut material?
Walnut poisoning (juglone) via compost and mulch is somewhat rare, but it can occur. Most often the poisoning occurs as juglone is released by the root system of the tree, and lateral migration within and somewhat beyond the tree's root zone carries it to susceptible nearby plants.
What type of pine trees do you have? Some are much more vulnerable to juglone poisoning than others. If you suspect that this might be your problem, then you can usually get your local county extension service or local university to assist you in identifying your pine trees, the nearby nut trees, and the probability that juglone poisoning is the cause of your problems. Sometimes a professor will haul a busload full of eager young students out to you property for a real-life case study. For free to you.
Your problem is probably not walnut poisoning, but it doesn't hurt to consider that possibility. It can be something much more simple such as a neighbor spraying a herbicide near the property line while you are off at work in the afternoon and some overspray is drifting to your pines. Or a neighbor intentionally killing the trees for some nefarious reason. Etc.
Good luck, Gideon
PS: Just last quarter I paused near an open door to a small lecture hall and observed as one of our Ag. Eng. professors was presenting a case study to a class full of eager upper-class students. Basically, in the case study, somebody had had great success growing tomato plants for many years but suddenly his plants were dying after he had moved the bed about 20 feet from its location from previous years.
Questions from the students slowly painted a difficult quandary: Same cultural variables, same fertilizer, same tomato varieties and sources, even the same soil since he had transferred much of his super compost- enriched soil from the old bed.
As students asked more and more questions, variables were eliminated and more subtle hints were dropped, but these eager young natural science & ag. engineering students just weren't catching on. Finally the instructor pointed to me smiling in the open doorway at the back of the room and asked if I had a not-too-obvious hint or question. I just said, "any unfriendly roots in the 'neighborhood'?" and 4 or 5 of the more astute students quickly shot their arms into the air. They had all heard briefly about walnut root zones and juglone as freshman, but just these 4 or 5 had retained that vague memory.
Once again, good luck with your problem.
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I have (or had) five pine trees (and another 20 as a fence). Two years ago one of the pine tree's leaves started to go brown and then 6months later was completly dead (it was around apx 10-12 years old), I then chopped it down. Then last year the one next to it did the same thing and yet again it is dead. I have two others next to it but, touch wood (forgive the pun), they are OK. An additional fact is that squirals have nexted in them, but squirrals have been around for years as I live backed on to a park.
The tree up to and at the point of dying look ok. Bark was find not signs of mold/fungus. However, after one did hugh amounts of scary looking mushrooms grew.
Can anyone suggest what may be causing this?
WayneL