Disfigured Maple Leaves May Be Due To Maple Tar Spot Disease

Fallen leaves infected by Maple Tar Spot – Image (c) JMcCt, 2017 all rights reserved – Click to view larger image

Compiled by The Bedford Citizen

Maple trees around Bedford have begun to show signs of Maple Tar Spot disease.

Distinctive blackened and shriveled leaves are dropping from trees along Maple Street and Fletcher Road in Bedford center, in West Bedford neighborhoods, and along Wagon Wheel Drive.  There is also some evidence of dropped leaves at the entrance to Town Hall. While the malady can affect all types of maple trees, it is commonly found in Norway, silver, and red maples.

Dennis Freeman, the DPW’s Assistant Tree Warden, shared information that indicates that the fungal disease affects the tree’s leaves, but not its overall health; in fact, it is considered by some to be a minor affliction.

While perhaps a minor arboreal disease, the impact on trees can be dramatic. Maple Tar Spot begins with small yellow spots that soon turn into blotches that cover the leaf surface, turning it a crispy mud-brown and causing early leaf drop.

According to Internet resources, the cause of the disease is a fungal pathogen of the genus RhytismaR. acerinum, R. americanum, or R. punctatum. The spores are spread by the wind, and it is possible for trees to be reinfected from season to season when leaves are left on the ground through the winter.

The web considers community engagement to be the best preventive control for Maple Tar Spot.

Raking fallen leaves is crucial, then bagging them for proper disposal. Mulching downed leaves when cutting the lawn can introduce the spores into the soil, and home compost piles typically do not generate sufficient heat to destroy the fungi.

Excess moisture is thought to exacerbate a tree’s tar spot infection over time. Eliminating any standing water or bark mulch piled high around the affected tree is suggested. For younger trees, the Internet recommends an application of fungicide such as triadimefon and mancozeb in the spring, when the buds appear and then at 7 and 14 days later.

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