Apple Tree Leaves
I live in NJ. I have an apple tree. Tree leaves have yellow spots that turn into brown spots and underneath brown spots there are thorns. What's that and how to treat?
For positive identification, take a sample of the leaves to your local agricultural extension office. It might be ''shot-hole'' disease, discussed in this article: https://www.gardeningknowhow.com/plant-problems/disease/shot-hole-disease-fungus.htm