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24-12-2025 17:08

Hulda Caroline Holte

Hello, I have found this propoloid ascomycete on

24-12-2025 18:12

Ethan Crenson

Hello all, A friend found this Orbilia growing on

23-12-2025 11:27

Louis DENY

bonjour forum,sur débris de bois de feuillu (acer

20-12-2025 10:49

Mirek Gryc

Hi. „I doubt it is possible to identify this ti

23-12-2025 08:27

Josep Torres Josep Torres

Hello.Small, yellowish ascomata, with very short a

21-12-2025 09:32

Josep Torres Josep Torres

Hello.A tiny ascomycete found embedded in wood in

21-12-2025 21:32

Pol Debaenst

Hello, Garden, Burgweg 19, Veurne, BelgiumOn 10/1

22-12-2025 23:38

Patrice TANCHAUD

Bonsoir, récolte sur un mur en pierre, apothéci

21-12-2025 12:34

Castillo Joseba Castillo Joseba

me mandan el material seco de Galicia (España) 

22-12-2025 00:47

Patrice TANCHAUD

Bonsoir, récolte à proximité du milieu dunaire

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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