Pine Devastation

Last summer I wrote about the saw fly attack on my white pine trees. If you remember, the branches were twitching with the movement of so many saw fly worms on each branch. If I shook a branch on my 4 foot tree, dozens of worms would fall off. I got some pesticide but by the time I got back, nearly all the branches were eaten off the pine tree on the north side. Somehow, many of those worms crawled to the east side of the house and had eaten a third of the needles off that 5 foot white pine tree. I sprayed and they all fell to the ground. I thought the tree on the north side might be doomed but maybe the other one had a chance. This spring both trees looked like they might make it. The one on the north side looked like a bottle brush - bare branches and green needles at the ends. But in the past couple weeks, all the branches were eaten off again. The white pine on the east side, the healthier one, is showing damage too. And it's not just my yard. Neighboring yards with tall white and red pines are turning brown. All of the pines bordering Highway 47 in the Rum River Scout camp look like they are turning brown and dying. There is a stand of pine trees bordering Elmcrest park - they've been hit too. What is going on here? Is it the saw fly devastation again? Did the saw flies lay eggs on the pine trees that have hatched and are munching these beautiful trees to death? I am on the DNR mailing list and they mentioned the danger of saw flies on pine trees. If all these pine trees die, I will be so sad.