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Leaves Dropping Early Due to Wetness, Disease

August 28, 2011 - Farmington — A wet, cold spring and several foliage diseases are causing some trees to lose their leaves this summer, state officials said.

During the past few days, people have brought the darkened leaves to the local University of Maine Cooperative Extension office, said Lauren St. Germain, home horticulture coordinator.

The wet spring and temperatures made conditions ripe for a fungal attack of the newly opened buds on the maples, she said. Some maples develop black spot on leaves that looks like lumps of tar. It starts out yellow and turns black.

The anthracnose fungus, while seen more in coastal areas, has also affected trees inland, making leaves drop early, St. Germain said.

Noticeable leaf-curling and leaf drop have been reported on ornamental maples from Kittery to Millinocket during late July and August, Maine Forest Service district forester Patty Cormier said.

“I've seen scattered occurrences throughout Franklin County in my travels, some areas more densely affected than others,” she said.

“Overall, trees are just like people, if they are not getting enough of what they need, or are under stress, insects and diseases are the wolf at the door!” Cormier said.

Conditions for the fungal development in May were best with the high moisture and at the time when trees are under stress from not only the wet, cold conditions but also the energy they use to develop new foliage, she said.

Why some trees and not others? That's the hardest question because there are so many variables, she said. It can depend on how well suited the tree is to the site it's growing in, the weather, air circulation, soils, drainage and other stresses to the tree.

The good news is leaf spot and anthracnose diseases rarely cause significant long-term damage, according to the forestry service. Most trees inspected this summer are expected to leaf out normally next spring.

If the disease happens two or three summers in a row, then the tree may be at risk, Cormier said.

“Sanitation is the big thing," St. Germain said. "These leaves should be raked and either burned or treated like trash,” she said. The fungus spores can carry over the winter on the leaves so they need to be burned with appropriate fire permits or composted by burying the leaves and covering them with a layer of grass clippings.

People can prevent the disease with fungicide but experts don't recommend it, she added. Trees are so big and it can be costly, she said.

As for potential of fall colors, “the amount of the brilliance of the color depends on the weather before and during the time that chlorophyll production is slowing down," Cormier said. "Temperatures and moisture in the soil can also affect the amount of color. Warm, sunny days and cool nights bring on the best for colors. Moisture in the soil plays a role in that a drought in late summer results in more dull colors and too much moisture has much earlier color and leaf drop.”


Ann Bryant, Sun Journal, August 2011


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