Tuesday, September 27, 2011

Fall color—and the lack thereof

A good thing we visited the fabulous Pumpkinville (above) last week, because these pumpkins are providing the blast of brilliant autumnal hues we usually expect from our trees—a blast that will be somewhat dimmed this year.

Not all the maple trees in Western New York have the dreaded tar spot, or the Rhytisma acerinum fungus, but enough do that leaf peepers will notice a considerable amount of dull brown patches along local roadsides this fall. Norway, red, and silver maples are said to be the most affected, but it seems more widespread than that this year—at least to my unscientific eyes.

And here’s the depressing prognosis, courtesy of the Purdue Extension:
Tar spot diseases seldom are detrimental to the overall health of infected trees. Tar spots may cause premature defoliation, but are not known to kill trees. Tar spot diseases are best managed by raking and destroying fallen leaves because the fungi overwinter on leaves.

According to all sources, the tiny spores infect the leaves in the spring, and their growth is much aided by very wet springs, as we had this year. (Apparently, Buffalo got the lion’s share of its annual rainfall in May.)

I also saw this on the University of Maine’s extension site: If infected maple leaves begin to crinkle and turn brown, anthracnose, another common disease of maple, may also be present. This must surely be the case, as I’ve noticed the spots before, but never as bad as this, and there is crinkling.

Sources agree that treatment is unlikely to help, and in any case would mean blanketing the city with fungicide. The municipality is unlikely to ever remove the infected trees, as the disease will not kill the trees. So I am stuck with ugly trees and their horrifically ugly leaves in front of my house pretty much every year.

I’m not alone. Tree owners throughout the Midwest and Northeast are asking their extension services about this, if google is any indication. Here's my answer: don’t plant Norway maples, and replace those you can with a good mix of other tree species. All trees get diseases and infestations, but if we don’t depend on a monoculture of just one type of tree, the impact is not as dire. I wish the people who chose to plant my block almost entirely with Crimson King Norway maples had thought of that!

Leaf spot photo by JP Thimot.


Anonymous said...

I used to have a dogwood with anthracnose. I found removing the fallen leaves in the fall did wonders even without spraying.


Janey said...

Hi Elizabeth,

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If you think your readers would like it too, please feel free to use it on Gardening While Intoxicated blog. There's code at the bottom of our post that makes it super easy to post on your blog. It's all free (of course). If you have any questions about posting it, let me know and I'll try to help.

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~ Janey

Claudia said...