Trees on the Hill

Maple trees in the area may have a fungus or tar leaf spot disease which can cause a tree to drop its leaves early in the year around July and August. This may have been caused by the extended periods of wet conditions we have been experiencing lately. It is not uncommon and has been seen in multiple areas across the county. So don’t worry, the maple trees are ok at this time.

Anthracnose (Colletotrichum gloeosporioides) refers to a group of diseases caused by fungi, and it can affect many shade trees. Similar fungi attack other trees such as sycamore, white oak, elm and dogwood trees. They cause a loss of leaves and are usually relatively harmless when the disease only strikes once.

Anthracnose spreads by airborne fungus and is especially prevalent during a wet or rainy spring. In maple trees, it is spread in April or May in most gardening zones. Wind blows through the infected trees and spreads spores onto new maple trees. Wet springs provide the ideal conditions for anthracnose spores to take hold.

Prevention: It’s important to rake up all the fallen leaves every autumn and compost them or burn them (if your area permits burning). Fallen leaves provide the ideal breeding ground for anthracnose. Another option is to have an arborist spray a special fungicide containing a chemical called mancozeb on the trees. If the damage continues year after year, it could predispose the tree to other problems.

It has also been noted that many honey locust trees have not been thriving. Honey locust are usually resilient however, they may host insect and mite problems (borer, plant bug, webworm, spider mites), which stress the tree. When the honey locust is stressed it makes it susceptible to invasion by fungi. The most aggressive canker disease of honey locust is Thyronectria canker. Symptoms include yellowing and wilting of the foliage, premature leaf drop, and stem dieback.

If you have concerns about the health of your trees, it is best to consult a licensed arborist for advice. If the street trees along the front of your property appear unhealthy or dead, contact Howard County’s Tree Division by email at, call 410-313-7450, or report the information via

Source: Donna Cosmato,

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