Leaves dropping from trees may signal a variety of things. Perhaps it is just a normal process, a sign of stress, or potentially a serious problem. Examine the situation a little closer to make a diagnosis as to the cause of trees dropping leaves.

For example, green leaves dropping from trees are often not a genuine problem and has been common this season. Trees often shed some green leaves shortly after leafing out simply because they have too many. Squirrels are also a common cause, especially clusters of leaves from nut trees such as walnut, hickories or oaks. Trees will also drop both green and brown leaves when under stress both from lack of water and if sitting in excess water. Recently planted trees may drop leaves due to transplant shock.

Look closely at leaves dropping and those still on the tree for spotting or discoloration. Foliar diseases causing early leaf drop has been common this season. The most common example is apple scab on flowering crabapples and apples. Spots initially are olive to gray and as they develop turn darker. Leaves yellowing and dropping will have lots of irregular black spots on them. Anthracnose causes irregular blighted lesions on leaves of many trees and is also common this year.

Trunk or root injury issues represent the most serious problems causing leaf drop, usually starting near the top of trees. Wilt diseases are one example visible now. Leaves will drop, but usually entire leaves will turn yellow, bronze, or brown first and do not have spots or lesions on them. Discolored foliage may also remain on trees for a period of time. Entire trees may turn brown and die because of serious diseases such as this. Examples include Dutch elm disease on elm, oak wilt on oaks, and verticillium wilt on numerous species, including maples.

Root and trunk injury can show remarkably similar symptoms, making diagnosis of wilts diseases difficult to confirm. Examine trunks of larger trees with wilting and dropping leaves for signs of injury, wounds, and hollow areas. Consider any digging, soil compaction, or construction activity that may have occurred not just in the past few weeks but in the past few years.

Finally, insect borers can also cause leaves to wilt and drop from trees. Borers as a group attack weak or highly stressed trees. One exception is ash infested with Emerald Ash Borer, which will attack perfectly healthy trees. Look for small D-shaped holes and pieces of bark falling as other symptoms.