Knowledgebase
Maple tree dying #407139
Asked June 14, 2017, 4:52 PM EDT
I have a very large Maple tree that has provided years of nice green leaves. This spring in upstate NY like most of New England was very wet. My Maple tree bloomed as usual but never fully developed the leafs. Now over 90% of the small leafs appear to be dead or dying. What may have caused this?
Brian
Wayne County New York
Expert Response
Hi Brian – there are a couple of possible causes of your maple tree’s loss of leaves. One potentially likely cause is an insect pest called the maple petiole borer. The petiole is the botanical name for the leaf stem, and the borers’ larvae burrow in the petiole in the spring, damaging it and causing it to break at that point. If the leaf drop is due to this borer you will see a darkened area on the petiole where the stem has broken. This insect will not harm the tree, and treatment is not recommended, as the tree will soon put out another flush of leaves. Here is some additional information about this insect pest:
https://entomology.ca.uky.edu/ef405
http://msue.anr.msu.edu/news/maple_petiole_borer_causing_leaf_drop_in_maple_trees
Another possible cause is a group of fungal diseases called anthracnose. The fungi infect young developing leaves during cool wet weather. If this is the cause of your leaf drop you will see dark brown to black water-soaked spots on leaves, and curled or cupped leaves. (If the leaves are entirely green when on the ground, then it is unlikely to be anthracnose, which would discolor or spot the leaves before dropping.) Although the disease can be somewhat unsightly, it is only a minor stress on the tree, and again, no treatment is recommended. As the weather becomes warm and dry, tree leaves will mature without infection. Once leaves are mature they are largely resistant to the anthracnose fungi. Even trees that have dropped many leaves due to infection will produce a new flush of leaves and recover with warm summer weather. Additional information about anthracnose here:
https://ag.umass.edu/landscape/fact-sheets/anthracnose-of-maple
You may also want to consult a certified arborist to assess the health of your tree. Here is a link to the Society for Arboriculture, which will help you find a list of certified arborists in your area.
