black spots and yellow leaves on crab apple tree
Our flowering crab apple tree is dropping leaves. Many leaves are yellow and have black spots on them. What is causing this? What can I do to stop this?
It sounds like you've got apple scab, a common fungal disease of crab apples and apples. Apple scab gets off to a great start with humid spring weather. Once it has spread, it's pretty futile to start spraying a fungicide. Rake up and remove all fallen leaves and fruit so that next year there won't be as much spore acitivity. Then start spraying a fungicide as soon as you see green tips on the buds next spring. You'll have to spray repeatedly, about every 7-10 days for two months. The good news is newer crab apple trees are bred for their resistance to diseases like apple scab.
