Observation 222386: Rhytisma acerinum (Persoon) Fries
When: 2015-10-25
No herbarium specimen

Proposed Names

61% (2)
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Recognized by sight
-28% (1)
Recognized by sight: Native host.

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Eye3 = Observer’s choice
Eyes3 = Current consensus


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Actually, for some reason this thing is very prevalent year after year
By: Andrew Khitsun (Andrew)
2015-11-15 20:39:54 CST (-0600)

in the city I live, and in the same areas too. Next year I will concentrate on other species of maple, and will try to find the other two species of Rhytisma and make sure I document the host.

By: Byrain
2015-11-15 10:46:28 CST (-0600)

I don’t have the literature or experience to say, but that Rhytisma acerinum being introduced with European maples seems to be the general idea. I just think Rhytisma are really awesome! :)

I’d like to see a phylogenetic tree on the group along with host and location information, but I don’t think there is much research on them out there because the damage done is only cosmetic and they don’t seem common in urban areas since fallen leaves are routinely cleaned up disrupting their life cycle.

Good reference, thank you.
By: Andrew Khitsun (Andrew)
2015-11-15 10:37:03 CST (-0600)

Are we on safe territory then talking about R.acerinum being on American soil and living on introduced from Europe species?

Norway maple
By: Byrain
2015-11-15 10:11:15 CST (-0600)

I found this which seems to explain the different between sugar and norway maples well – http://blogs.pjstar.com/...

I think this is a Norway Maple because all the lobes at the apex are sharp while, “Sugar maple with sharp points at the apex of each of five lobes while other areas have blunt points”. Additionally the texture of the tar spots seem closer to the Rhytisma acerinum than R. americanum photos in the Canadian reference.

Also see my observation 117549
By: Andrew Khitsun (Andrew)
2015-11-12 19:11:25 CST (-0600)

descriptions fit R.acerinum pretty well, with fruit bodies sometimes solid but covered by “pimples”, sometimes disintegrating into fields of dots in the middle but with some solid margin around them. So perhaps it’s right species but wrong maples? I mean Norway maples (European) with R.acerinum (European)?

So I keep digging. Beug & Bessette (2014) state that R.americanum grows on sugar maple,
By: Andrew Khitsun (Andrew)
2015-11-12 19:04:51 CST (-0600)

while R.acerinum grows on Norway maple, without mentioning R.acerinum growing just in Europe. Perhaps they imply that it immigrated together with Norway maple, which is well established around here. I will check my maples as soon as I can – the stuff I assume is sugar maple can actually be a Norway maple, for they’re highly invasive and supplanted native plants even in the forests, let alone within the cities. I always had difficulties telling the two apart just from leaves – while there are plenty of comparisons out there showing how Norway maple is pointier and has more lobes, in reality it’s hard to tell, for both species are variable. The seeds are different though, and Norway maple is supposed to have a white sap when you break a leaf stalk. If all the maples in the area are Norway instead of Sugar, then R. acerinum will look feasible on them, being brought from Europe. Beug & Bessett also say the spores are different, but I don’t have means to see that.

Host is Sugar Maple Acer saccharum
By: Andrew Khitsun (Andrew)
2015-11-09 21:11:33 CST (-0600)

Created: 2015-11-09 18:22:52 CST (-0600)
Last modified: 2015-11-15 10:11:28 CST (-0600)
Viewed: 57 times, last viewed: 2017-06-21 03:14:41 CDT (-0500)
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