You may spot a serious disease before it spreads by watching for yellow or brown leaves, early leaf drop, dead branches, peeling bark, cracks, black growths, mushrooms, or a thinning canopy. Common problems in Ontario include Dutch elm disease, oak wilt, black knot, apple scab, and anthracnose. Each condition creates a different pattern of damage. One change does not confirm a disease. Drought, insects, root damage, poor soil, and weather stress can cause similar symptoms. A trained professional must examine