Everyone knows my small problem with the garden plants clashing with the lawn being spot sprayed with 2,4-D; if not see here! My question being this; I bought a new backpack sprayer this spring, first year I've used it and if you keep it pumped up with pressure it sprays at a higher velocity, just common sense. Here's my theory and this comes from knowledge of spraying varnish with a spray gun. I build furniture and finish it by spraying the varnish on and it; in this particular field the higher the PSI the more "overspray" which is what it's called but in lawn care I'm assuming its the same thing just different word called "Drift" but for a reason. If it drifts in the wind it could kill wanted plants. My solution, since I am "spot spraying only" if I don't pump the pressure up on the backpack sprayer would I have less drift the same as with spraying varnish the lower the PSI the less overspray?