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02-07-2025 18:45

Elisabeth Stöckli

Bonsoir,Sur feuilles d'Osmunda regalis (Saulaie),

02-07-2025 17:26

Yanick BOULANGER

BonjourRécolté sur une brindille au fond d'un fo

02-07-2025 09:32

Nicolas VAN VOOREN Nicolas VAN VOOREN

Hello, bonjour.Here is the paper I'm searching for

30-06-2025 16:56

Lydia Koelmans

Please can anyone tell me the species name of the

01-07-2025 23:37

Josep Torres Josep Torres

Hello.A Pleosporal symbiotic organism located and

30-06-2025 12:09

Edvin Johannesen Edvin Johannesen

This tiny, rather "rough" erumpent asco was found

30-06-2025 06:57

Ethan Crenson

Hi all, Another find by a friend yesterday in Bro

30-06-2025 19:05

ALAIN BOUVIER

Bonjour à toutes et à tousJe cherche à lire l'a

30-06-2025 14:45

Götz Palfner Götz Palfner

This is a quite common species on Nothofagus wood

25-06-2025 16:56

Philippe PELLICIER

Bonjour, pensez-vous que S. ceijpii soit le nom co

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Black dots on maple leaf
Alan Rockefeller, 31-12-2013 11:00
Alan RockefellerGrowing on Acer macrophyllum (bigleaf maple).  Seen at the Yuba Watershed Fungus Fair.

No asci observed. Many parathyses with tiny oil drops were seen, they measured 30 – 45 × 2 – 3 micrometers. Many clavate basidia-like things seen, however they never had sterigmata or spores inside. Those measured (28) 36 – 47 x (5) 7 – 8 micrometers.

  • message #26494
Jacky Launoy, 31-12-2013 12:58
Re : Black dots on maple leaf
Rhytisma acerinum (Pers.:Fr.) Fr.
David Malloch, 31-12-2013 15:34
David Malloch
Re : Black dots on maple leaf
Hi Alan..
That is probably Rhytisma punctatum.  The US host-index lists it on Acer macrophyllum in California, Oregon and Washington.  The "clavate, basidia-like things" are probably immature asci.  These would be mature in the spring at about the time the new leaves are emerging on the tree.

Dave
Byrain, 31-12-2013 16:47
Re : Black dots on maple leaf
Alan, I found that leaf and posted it on MO as Rhytisma punctatum.  I have the other two leaves from that collection also.  I scoped them too and also saw no mature asci.

Here are some more macro images... http://mushroomobserver.org/156379?q=1higi?

Edit:  I understand that punctuate dots like this on Acer macrophyllum = R. punctatum, but there is another species with a somewhat similar appearence on other maples.
http://www.glfc.forestry.ca/VLF/ForumPresentations/hsiangtarspot_08e.pdf