Foliage Problems

We have had some pretty wild threads regarding fire protection, brush cutting, and even converting engines to oil. One thing that has not been discussed is chemical control.
As I recall, in the steam days, they ran weed spray trains to help contain some of the foliage along the right-of-ways, especially here in the east.
Also in 1997 Les and I video-taped one on the Tennessee Pass Line, which we felt was odd considering the line was about to be mothballed in a few months, which it was.
So, my question is, did the D&RGW ever use chemical sprays to inflict damage on the foliage along the tracks on the narrow gauge, and when did it stop.
Could it be that due to health and other ecological concerns that they are not used any more.
Further info and thoughts appreciated.
Greg Scholl
PS...My point here is that perhaps we didn't hear about many fires in Colorado during steam days, because the weed spraying might have assisted in keeping the foliage down.