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17-03-2026 19:41

Pyréno sur branche morte de chêne
Bernard CLESSE Bernard CLESSE

Bonsoir à toutes et tous,Pourriez-vous m'aider à

12-03-2026 19:44

Ostropoloid fungus on Hibiscus
Enrique Rubio Enrique Rubio

Hi to everybody.Can you give me any suggestions ab

17-03-2026 10:09

Lasiobelonium corticale ?
François Freléchoux François Freléchoux

Bonjour, Voici la description rapide d'un petit d

17-03-2026 10:40

Geopora sumneriana
Martine Vandeplanque Martine Vandeplanque

Bonjour à tous.Chaque année en mars ou avril, il

05-03-2026 10:07

White apothecia on pine cone
Hulda Caroline Holte

Hello, I found and collected this species growing

12-03-2026 15:45

Dematioscypha cf. olivacea
Åge Oterhals

Dear forum,I found this small discomycete on a ver

12-03-2026 16:17

Mollisia atlantica
Sylvie Le Goff

Bonjour à tousRécolté dans le 22 en France (ré

11-03-2026 17:36

Help for Genus and Species ID
Michel Hairaud Michel Hairaud

Bonjour, Je cherche des indices  pour cette réc

14-03-2026 13:51

Phylloscypha sp
Thierry Blondelle Thierry Blondelle

Hi everybody Under Quercus ilex, i hesitate to na

08-03-2026 14:05

Helvella lacunosa
Thierry Blondelle Thierry Blondelle

Bonjour à tous,Sur 3 récoltes supposées de H. l

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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