PHP, if you see dead whole trees or trees with rolled, twisted, or cupped leaves [see picture], it may be caused by chemical or herbicide drift. Over 70% of PHP is farmed by large commercial Ag producers with little local regulations and oversight. Unfortunately, the heavy reliance on toxic pesticides, herbicides, and artificial fertilizers affects PHP residents, wildlife, and the landscapes at multiple levels. Drifts can spread in a 1-mile radius . Herbicide-impacted trees.