Some homeowners are experiencing problems with their maple trees. The trees are turning colors and dropping leaves in late July or early August for no apparent reason. A study conducted by North Dakota State University looked into this early coloring and leaf drop on the maple, as well as other shade trees. The researchers determined that there were different causes for this problem.
Many homeowners speculated that the maple trees prematurely turned color and dropped leaves because an early fall or winter was coming. According to North Dakota State University, this is not the case. Trees depend on length of sunlight they receive and not the weather to determine when to prepare for winter. As the daylight gets shorter, the maple tree begins to store food, taking those resources away from the leaves. Once the leaves get deprived of a food source, they begin to change color and drop. Since early winter or colder weather were not the cause of yellowing and early leaf drop, researcher had to look at other possible causes.
One theory of why maple trees turn color early and begin to drop leaves off of some limbs is attributed to squirrels. The squirrels eat away the bark at the base of the limb causing the limb to lose access to food from the trunk of the tree. These limbs will not recover from this damage caused by the squirrels. You should cut the limb at the base so it does not affect any other part of the maple tree or unexpectedly fall.
The researchers also determined that early leaf coloring and drop was being caused by a fungus attacking the maple trees. A disease known as Verticillium wilt was infecting the maple tree causing it to prematurely turn colors and drop leaves. According to the research, the fungus begins to infect one or two limbs before attacking the rest of the maple tree. However, some research indicate that the fungus can cause the entire maple tree to turn yellow and drop leaves. There is no known cure for this disease, but you can prolong the life of the maple. Remove any dead or yellowing limbs at the base of the limb. Use fertilizer in the fall after the first frost. Both of these treatments will prolong the life of the maple, but eventually the maple tree will die.
A third thing that researchers determined could cause the early yellowing and leaf drop on maple trees is insects. Aphids and other types of sucking insects enjoy cool, moist weather and reproduce quickly in these environments. An early cooling period can cause these insects to infest maple trees and suck the sap, causing early yellowing and leaf drop. A good sign that your maple tree has been infested by these insects is the dropping sap found under the tree. A sticking, black and sooty substance will begin to accumulate under the limbs of the maple tree when these insects infest the tree. The insects prevent the tree limbs from getting the food resources from the trunk of the tree and eventually yellow or color, then drop off.
The researchers from the university did not eliminate other possible causes of early coloring and leaf drop. Maple trees located close to highways and roads also have a tendency of changing colors early because of the road debris. Other cause can come from root problems within the maple tree, unknown diseases and other possible environmental factors not researched. Not everything is known about this premature maple tree condition, but when a tree does begin to show signs of this problem, you must have the maple tree inspected.