Answer: If it is not greening up, even after using fertilizer, it must be stress in other ways. You didn't mention whether or not you've pruned your tree. Pruning encourages new growth, which should be healthy if the roots are healthy. Try pruning a few branches. If the new growth still does not look healthy, the tree may be diseased. I can't diagnose the problem long distance so I can only suggest you take a sample branch with leaves to your local extension office. Helpful folks there can inspect the leaves and twigs and determine just what the problem might be. They can also suggest remedies for your crab apple. Best wishes with your landscape!
Q&A Library Searching Tips