Slightly tangential, but in the good old days of the CEGB they had one or
more experts in herbicides which are used in quite widely substations and
other place as well as to suppress shrub and tree growth under transmission
lines. In the '80s, the CEGB was doing research on "expert systems",
computer programmes to capture "expert knowledge", and of a number of
applications investigated, this problem was the only one which worked really
well. I forget the details, but apparently there was quite a lot of skill in
selecting the optimum herbicide depending on the type of soil, type of weed,
time of the year, weather conditions etc.