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13-01-2026 07:57

Danny Newman Danny Newman

cf. Bombardia on indet. decorticate woodAppalachia

11-01-2026 20:35

Josep Torres Josep Torres

Hello.A very tiny pyrenomycete sprouting sparsely

13-01-2026 10:13

Danny Newman Danny Newman

Cordieritidaceae sp. on indet. wood w/ Hypoxylon s

13-01-2026 07:28

Danny Newman Danny Newman

Chlorociboria glauca on indet. decorticate logThe

13-01-2026 07:14

Danny Newman Danny Newman

Neodasyscypha cerina on indet decorticate logThe S

13-01-2026 09:10

Danny Newman Danny Newman

Dasyscyphella chrysotexta on indet. decorticate ha

13-01-2026 08:43

Danny Newman Danny Newman

Tricladium varicosporioides on indet. decorticate

13-01-2026 08:49

Danny Newman Danny Newman

Coccomyces sp. on fallen Rhododendron leavesPretty

12-01-2026 22:02

Ethan Crenson

Hello all, I am hoping someone will have some ins

13-01-2026 07:51

Danny Newman Danny Newman

Atrocalyx sp. on indet. herbaceous stemAppalachian

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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