This drove me nuts every year, as an applicator. In late October many of the lawns would have leaves--very frustrating.
Nothing solved the problem. Sometimes I just postponed their treatment and had to drive back out to the site a week or two later. I would leave a note--"Call me when leaves are raked." They wouldn't call--or --they would call at 3 pm and say come right away before more leaves fall. "My lawn man said he would come on Monday--but he is not sure."
Sometimes I applied the granules, and billed them and said I would return and redo areas where leaves were too deep, (thereby waiting two weeks, until it was convenient for me). At times I applied liquid and had to return in a couple weeks to redo parts--but by then I had switched over to granules.
What percent of the granules get through the leaves? What percent are picked up? No one knows. What happens if rain on top of granules, on top of leaves?
Any suggestions? What works the best? (Profit wise?)