Arent you in the end of growing season?
I dont do anything to infections in the end of the growing season. The leaves Will drop anyway.
We had the summer dormanr period and now are a couple of weeks into the second growing period. It usually lasts until end of October when the leaves start to change. The maples have new shoots springing out now. The azaleas have suckers a foot long that started growing a couple of weeeks ago.
Usually the trees don't grow much mid August to mid September because the days are long and hot, 95F to 100F or hotter three or four weeks, 35C to 38C. I used to think the dogwoods out in the yard were dying, but they spring back just fine.