You are not going to be able to reach 80 feet unless you have a pretty powerful
hydraulic sprayer. I used to use a bean 400 psi sprayer with a 100 gallon tank
and I struggled to reach the 20 foot trees in the permanent plantings. You
would need something very heavy duty to reach. Not sure whether bordeaux will
work to well or if you could even find it anywhere these days.

toad