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03-02-2026 20:44

Mycoparasite with irregular conidia
Zetti Mario

When I first saw this white mould on an Agaricus s

18-08-2025 15:07

pyrenomycete on dead parts of foliose liverwort from Norway
Lothar Krieglsteiner Lothar Krieglsteiner

.. 20.7.25, in subarctic habital. The liverwort i

02-02-2026 21:46

Dark disc on Populus
Margot en Geert Vullings

On a barkless poplar branch, we found hairy discs

02-02-2026 14:55

Lichénicole sur Lobaria
Andgelo Mombert Andgelo Mombert

Bonjour,Sur thalle de Lobaria pulmonaria.Conidiome

02-02-2026 14:33

Lichénicole sur Peltigera
Andgelo Mombert Andgelo Mombert

Bonjour,Sur le thalle de Peltigera praetextata, ne

31-01-2026 10:22

Lichenicole hypocreale
Michel Hairaud Michel Hairaud

Bonjour, Cette hypocreale parasite en nombre les

02-02-2026 09:29

Scutellinia hirta ? sur souche moussue
Bernard CLESSE Bernard CLESSE

Bonjour à toutes et tous,Pour cette récolte de 2

01-02-2026 19:29

Lambertella sur Olea
Nicolas Suberbielle Nicolas Suberbielle

Bonjour, Marie-Rose D'Angelo (Société Mycologiq

30-01-2026 22:49

Calycina ?
éric ROMERO éric ROMERO

Bonjour tous, Récolté dans les Vosges le 22/10/

31-01-2026 09:17

Small hairy discs on Castanea
Marc Detollenaere Marc Detollenaere

Dear Forum,On decorticated wood of Castanea,I foun

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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