Hello all:

The last owner of my home used weed killer at the base of three mature pine trees in the backyard in an attempt to kill weeds growing in the area. Since then, the trees have many brown needles, and their needles are less dense (analogous to a man with thinning hair).

I have many other mature pines in the yard, all vibrant and healthy. Can I do anything to restore the three sick trees to their former health?