Q: Our crab apple tree is suddenly losing all of its leaves. Some are yellow, some are green, and some have large brown spots on them. The lawn next to the tree is irrigated, so we think the tree is getting enough water. What else can we do?
A: It sounds like the tree has a fungal disease called apple scab. It is a common disease on older apples and crab apples. Most newer varieties have some resistance to the disease. Resistance doesn’t mean they won’t get the disease; it just means that they will have less of the disease in many years when the conditions are right for the disease to develop. In some years, the conditions are so good that the disease is a problem for all but the most resistant trees.
