The Journal Gazette
Sunday, July 14, 2019 1:00 am

Wet weather-caused fungus menaces sycamores


In the last several years, northeast Indiana residents watched as countless ash trees gradually lost their leaves and died from infestation with the emerald ash borer.

In the last few weeks, some people have noticed another species of tree looking a little sickly.

As other trees leafed out, these didn't follow suit. And if they did get leaves, the trees tended to drop the leaves soon after. 

The trees are sycamores, and the problem, tree experts say, is a blight known as anthracnose.

Yep, there's a fungus among us, and sycamore trees are its playground.

“Sycamores took a real beating this year,” said Lindsey Purcell, an urban forestry specialist and director of the Indiana Arborist Association. 

He pins the blame on this year's prolonged wet and cool weather. The weather created “extremely favorable conditions” for the fungus to thrive, he said. 

But the situation for sycamores is not as dire as that faced by ash trees, said Terri Theisen, horticulture educator with the Allen County Purdue Extension office.

Trees with anthracnose, she said, probably aren't dead – at least not if this year is the first time the condition has occurred.

“If people think their tree is dead because it dropped all its leaves, don't take a chain saw to it yet,” she said. “If it's an otherwise healthy, big tree, it's probably just cosmetic (damage). We really think you should give it a chance.”

Now that the weather has turned warmer and somewhat more dry, trees should start to leaf out again, Purcell said. But branches affected by anthracnose won't rejuvenate, he said, because the fungus affects the ends where new growth starts.

People with sick sycamores can prune affected branches back to the last live leaf or bud to improve air flow and should water and fertilize trees at the roots, said Purcell, who also teaches at Purdue University in West Lafayette.

But the trees don't need to be sprayed or treated at this point, he said.

“The best thing for a tree owner is patience,” Purcell said, adding sycamores will probably rebound next year if weather doesn't interfere.

“Sycamores are efficient at storing nutrients in their trunk,” Theisen said. That helps them recover, she said.

But the trees could suffer demise if faced with similar wet and cool conditions several years in a row, said Derek Veit, superintendent of forestry operations with the Fort Wayne Parks and Recreation Department.

It's not the fungus that will kill the trees, he said, but the trees will weaken, making them susceptible to other pests.

Still, the parks department has had to remove few, if any, sycamores this year, Veit said. There are 742 sycamores serving as street trees and many more in parks and along riverbanks, a favored habitat, he said.

“It used to be you could look along the riverbanks and you'd see dead (sycamore) trees,” he said. “I kept thinking, 'These trees are goners.'

“But then I realized, if these trees have been there 100 years, they've probably seen worse conditions.”   

But, as with many things botanical and horticultural, the wild card for sycamores is a changing climate, Theisen said.  

If more years are like this year, or if the weather stays warmer longer, that could change the relationship of the fungus and its host, she said. Anthracnose tends to appear in cycles, Theisen said, about once every 10 years for a more severe outbreak.

“Climate change can affect those (cycles) as well,” she said. 

This year, the local extension office has received a bumper crop of plant samples being affected by all kinds of fungal diseases, Theisen said, including leaf spot and early blight on tomatoes, tar spot on maples and recently, powdery mildew on the leaves of perennial flowers.

So it's not just sycamores that are suffering from the weather, she said.

And, as with other fungal problems, gardeners should practice good hygiene when disposing of anthracnose-infected leaves and branches, Veit said. Don't just discard them in a home compost pile if you want to avoid propagating the pest, which spreads through spores, he said. Burning is a good disposal method, although open burning is not allowed in the city, he pointed out.

Next year, before leaf-budding, the trees can be treated with a fungicide, Veit said. If a tree does die, he added, it can be replaced with a species known as London plane tree, which is a cross between two sycamore species and has a greater resistance to the fungus.

Sycamores may be hard to find at local garden centers today because of the pest problem, Veit said.

If anthracnose recurs next year, Theisen said, get help.

“After two years, you should definitely get an arborist to come out and look at the tree,” she said.

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