The tree I am concerned is a Red Star peach in south-central Wisconsin. It was planted in an orchard tended by a teacher-parent group at a nearby elementary school.
Stone fruit and especially peach seems like a dodgy thing this far north, but people are doing it anyway. This tree was going great, approaching its 3rd season producing fruit when it developed a big fat canker exuding sap in the crotch of the trunk where the two main branches fork out. Early in Spring, I applied a conservative non-chemical treatment of excising the canker with an X-acto knife.
Now, the trees started to curl, get bumps on them, with some of them now black and withered. Don’t know if the tree budded more leaves, and a Wisconsin Extension person once told me trees can do this, but there appear to be fresh leaves on the tree without this problem.
Don’t know if this is fungal or a mite outbreak, but my wife grew up on a farm and told my how to look for mites by blowing on the leaf and looking for movement, and I didn’t see any activity, so I think this is fungal.
I also read that once the fungus gets to the leaves, there is nothing you can do apart from spraying in Fall to help bring the tree around next season. The tree is on a school yard managed by a teacher-parent group who “don’t want to use any poisons”, but maybe I can ask if I could apply copper as suggest earlier in this thread?
My question for now is that the tree has a heavy load of peaches “set”, and I am worried if this crop will put yet more stress on the tree to everything else happening to it. Is there any benefit to thinning the crop or removing it entirely? Is a stressed tree putting out an abundant crop and then perishing a “thing?”
Pulling those fruit-lets off the tree is something I can do without getting a bunch of people to agree on a chemical spray – the fruit matures in late July anyway before the students return, if they return depending on how Fall instruction will be handled in our district, so the fruit is pick-what-you -want anyway.