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29-06-2016 15:18

Per Vetlesen

HiIt was found on the bark of a dead branch of Jun

07-01-2018 22:47

Per Vetlesen

Grown in moist chamber on bark/resin of fallen Pin

06-04-2026 15:04

David Chapados David Chapados

Hi! Could someone help me identifying this specim

06-04-2026 21:36

Viktorie Halasu Viktorie Halasu

Hello, could anyone please send me the article wi

06-04-2026 19:40

David Gibbs David Gibbs

Help with this one much appreciated, on rotting Fa

06-04-2026 11:07

Louis DENY

Bonjour forum, Trouvé sur bois de feuillu très d

06-04-2026 16:24

Juuso Äikäs

Last Tuesday I found some tiny white Helotiales gr

05-04-2026 13:33

Sylvie Le Goff

Bonjour à tousPuis avoir votre avis sur ce champi

05-04-2026 20:40

Robin Isaksson Robin Isaksson

Hi!Found i Japan on bark of Abies sp. Spores 35-4

06-04-2026 08:15

Lothar Krieglsteiner Lothar Krieglsteiner

some days ago, on the lower surface of leaf of Que

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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