365 Urban Species. #250: Tar Spot

[urbpan]

Photo by urbpan. A fallen Norway maple leaf is marked with tar spot. Location: Olmsted Park, Brookline.

Urban species #250: Tar spot Rhytisma acerinum

Drops of tar or perhaps black paint seem to appear on the leaves of maple trees in late summer. The leaves become dry and may not turn the bright fall colors treasured by residents of New England, and our many seasonal tourists. The tar is in fact a fungus, this year an exceptionally common one, due to our very wet spring. Spores are produced by last years leaf litter, and infect the new spring leaves on the trees. Norway maple is especially succeptable to tar spot, and the fact that it is the most popular choice for new street tree plantings may be aggravating the spread of tar spot to our native maples. This year many of our maples are also infected with anthracnose fungi, which turn the leaves brown and burnt looking. Neither fungus usually causes the death of their host trees, but will cause premature leaf drop, and rob us of some of the dazzling display of autumn.



Close up of Norway maple tar spot.


Photo by cottonmanifesto. A silver maple leaf with tar spot.

Comments

[perspicuity.livejournal.com]

haven't seen a lot of that up here. then again, haven't much looked. mostly leaves are chewed on by critters, not crud :>

i imagine the people that loathe norway maples are overjoyed they're being crudded though. particularly invasive for a hardwood, and the wood is a strange yellow/orange color too. it's actually a pretty thing, it's just VERY over abundant with the near bamboo-like growth via the not exactly rhizome roots. chop chop chop begone! heck, they even have a special TOOL to pry the saplings out of the ground :)

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[chrono2501.livejournal.com]

I'd been wondering what those were. I've been on a few nature walks at the Morgan Arboretum (Montreal) and I only started noticing them this year.

Even today, they seemed to be countless among the maples around my residence. Hopefully they won't affect the trees next year round.

[wandererrob.livejournal.com]

Is that why all the maples around here look so rough the past few weeks? I've noticed dead spots on all the leaves, but hadn't looked that closely. I have however noticed it seemed to only be the maples.