Q.spraying insecticides on fruit trees
hi,
i am a new gardener planted new fruit trees.lately some insects where affecting my plum,nectarine trees and leaf curl on peach tree.I have used a spray insecticide on them after two to three days i saw leaf rust on them, I was wondering is it because of insecticide?! or any other reason. I also want to know can we spray insecticides on tree when fruiting?!,because i have sprayed it on peaches tree and its fruiting.is it harmful to eat those fruits now when they are ripen?!

This is more than likely a fungal issue, rather than an insect problem. I would apply wettable sulfur and dolomitic lime to the area to treat this problem. To treat the leaf curl, refer to this article. This article is for peaches, but since they are closely related, then the treatments will be similar: https://www.gardeningknowhow.com/edible/fruits/peach/peach-leaf-curl.htm