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16-05-2025 05:47

Francois Guay Francois Guay

I found this super tiny hyaline asco on fir needle

11-05-2025 10:22

Karl Soler Kinnerbäck

Found on moist Betula wood dipped in freshwater st

18-05-2025 16:49

François Bartholomeeusen

Dear forum members,On cow dung, between fruiting b

19-05-2025 14:34

David Chapados David Chapados

Hi, I'm trying to find the species of this specim

19-05-2025 10:00

Castillo Joseba Castillo Joseba

Me mandan el material de Galicia (España) , recol

19-05-2025 10:01

Castillo Joseba Castillo Joseba

Me mandan el material de Galicia (España) , recol

19-05-2025 10:00

Castillo Joseba Castillo Joseba

Me mandan el material de Galicia (España) , recol

18-05-2025 11:03

Castillo Joseba Castillo Joseba

Mer mandan el material seco de Galicia (España),Â

18-05-2025 11:07

Castillo Joseba Castillo Joseba

me mandan el material seco de Galicia,  (España)

16-05-2025 20:59

Jean-Paul Priou Jean-Paul Priou

Bonsoir à tous, un ami normand vient de me faire

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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