Black Tar Spot

(Rhytisma acerinum)

Conservation Status

 

No Image Available

 
  IUCN Red List

not listed

 
  NatureServe

not listed

 
  Minnesota

not listed

 
           
           
           
 
Description
 
 

Black Tar Spot is a parasitic fungus infecting several species of maple (Acer). In Minnesota it infects only Norway maple. It is often found in suburban locations, where its host is planted. It is somewhat tollerant of air pollution.

In the spring the infection appears as a yellow spot on the leaf. These turn first brownish-black with a yellow border, then, in late summer, black with a yellow border. The black spots resemble tar. The spots are solid, not a cluster of small spots. They may be up to 1½ in diameter but are usually much smaller.

 
     
 

Similar Species

 
 

Speckled Tar Spot (Rhytisma punctatum) causes dense clusters of very small black spots.

Tar Spot (Rhytisma americanum) infects red maple and silver maple.

 
     
 
Habitat and Hosts
 
 

Suburbs

Norway maple

 
     
 
Ecology
 
 

Season

 
 

Spring to fall

 
     
 
Distribution
 
 

Distribution Map

 

Sources

4, 26, 29, 30, 77.

Until 1998 this species name included what is now recognized as Rhytisma americanum. Some or all of the records represented on the map at left may be Rhytisma americanum.

 
  6/8/2022      
         
 

Occurrence

 
 

Uncommon in Minnesota because the host is uncommon

 
         
 
Taxonomy
 
  Kingdom Fungi (fungi)  
  Subkingdom Dikarya  
  Phylum Ascomycota (sac fungi)  
  Subphylum Pezizomycotina  
  Class Leotiomycetes  
 

Order

Rhytismatales  
 

Family

Rhytismataceae  
 

Genus

Rhytisma (tar spot fungi)  
       
 

The life cycle of this and most other fungi is pleomorphic. It has both an asexual reproductive phase (anamorph) and a sexual reproductive phase (telemorph). Each phase is often morphologically distinct. In the past, the International Code of Botanical Nomenclature allowed each phase to be assigned a different scientific name. It was incorrect to refer to the anamorph phase by the telemorph name, and vice versa. Some mycologists and molecular biologists consider this practice to be obsolete. Molecular phylogeny allows the accurate placement of a species in any part of their life cycle. On July 30, 2011, at the meeting of the XVIIIth International Botanical Congress in Melbourne, Australia, that practice ended. Prior to that meeting, the early, anamorphic phase of this fungi had been named Melasmia acerina. Both phases are now named Rhytisma acerinum.

 
       
 

Synonyms

 
 

Melasmia acerina

Xyloma acerinum

 
       
 

Common Names

 
 

Black Tar Spot

European Tar Spot

Sycamore Tarspot

 

 

 

 

 

 

 

 
 
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Slideshows
 
Rhytisma acerinum - fungi kingdom
Nineli Lishina
   
 
About

Published on Jan 25, 2015

Rhytisma acerinum - fungi kingdom

 

 

slideshow

       
 
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Other Videos
 
  Insights into Nature - Tar Spot Fungus on Sycamore
Roger Griffith
 
   
 
About

Published on Oct 27, 2014

The Tar Spot (Rhytisma acerinum) is a very common ascomycete fungus that typically grows on Celtic Maple / Sycamore (Acer pseudoplatanus) leaves giving a prominent black spot or spots on the leaf lamina, upper and lower epidermal surfaces. It is reported to grow occasionally on Norway Maple (Acer platanus) leaves.

   

 

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