Tuesday, August 25, 2009

Horse Chestnut

If you walk through the cemetery right now, you might think that fall is coming early.
Some trees are losing their leaves,
and when you crunch through the leaf litter, it smells like fall. It turns out that only the horse chestnuts are dropping their leaves, but it's not because their yearly schedule is off. They have anthracnose. That's an umbrella term for diseases of hardwoods caused by a group of related fungi. It seems that the cemetery only has a problem with the fungus Glomerella cingulata, known to attack horse chestnuts; I haven't seen evidence of anthracnose on any other type of tree.

The fungus starts out by killing spots on the leaves.
These spots grow bigger...
and eventually the entire leaf dies.
There are some trees with not a bit of green left. Although the fungus won't kill a tree, the defoliation will weaken it over time. The horse chestnuts in Green-Wood appear to be strong, though. They've managed to bear fruit despite their infection.


  1. Is this what affects the plane trees in my neighborhood, which drop an abundance of brown, dry leaves every August? Incidentally, not far from Green-wood.

  2. It very well could be. Some of the plane trees are affected in the cemetery as well. Here's an article with more info/some pics.

  3. Seed production can actually be a sign of stress, too -- if a tree has been taxed year after year, and has been weakened enough by anthracnose or some other disease, it may flower heavily and put out a bumper crop of fruit/seed in an attempt to reproduce and pass along its genes to a new generation before it dies.

  4. That's interesting, Deb. I wonder if they are fruiting earlier or more profusely than they normally would.