Was chatting with a friend this week who informed me of another local company once having an issue with the PG. Apprently they had some problems tracking/striping herbicide on lawns that were not sprayed. Basically the scenario is that you use the PG to spray lawn A with a broadleaf herbicide , then the next morning apply granular on lawn B. If the turf was a little wet, the herbicide from yesterday remaining on the tires becomes tracked to lawn B. This could possibly happen, but by the same token I never clean my spray boots at end of each day either.