Willow Tar Spot

(Rhytisma salicinum)

Conservation Status

 

No Image Available

 
  IUCN Red List

not listed

 
  NatureServe

not listed

 
  Minnesota

not listed

 
           
           
           
 
Description
 
 

Willow Tar Spot is a parasitic fungus infecting several species of willow (Salix). In Minnesota it infects prairie willow, pussy willow, and possibly Bebb’s willow and other willow species. It has not been recorded on crack willow or other willow tree species. It is intollerant of air pollution and is usually found in rural locations.

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 more than 1 in diameter but are usually smaller, due at least in part to the narrow width of the leaves it infects.

 
     
 

Similar Species

 
     
     
 
Habitat and Hosts
 
 

Prairie willow, pussy willow and possibly Bebb’s willow

 
     
 
Ecology
 
 

Season

 
 

Spring to fall

 
     
 
Distribution
 
 

Distribution Map

 

Sources

4, 26, 29, 30, 77.

 
  6/8/2022      
         
 

Occurrence

 
 

Widespread and locally common

 
         
 
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 salicina. Both phases are now named Rhytisma salicinum.

 
       
 

Synonyms

 
 

Melasmia salicina

Xyloma leucocreas

Xyloma salicinum

 
       
 

Common Names

 
 

Willow Tar Spot

 

 

 

 

 

 

 

 
 
Visitor Photos
 
           
 

Share your photo of this fungus.

 
  This button not working for you?
Simply email us at info@MinnesotaSeasons.com.
Attach one or more photos and, if you like, a caption.
 
 

 

 
 

 

 
           
           
 
MinnesotaSeasons.com Photos
 
 

 

 
           

 

Camera

     
 
Slideshows
 
 
     
     

 

slideshow

       
 
Visitor Videos
 
       
 

Share your video of this fungus.

 
  This button not working for you?
Simply email us at info@MinnesotaSeasons.com.
Attach a video, a YouTube link, or a cloud storage link.
 
 

 

 
     
     
       
       
 
Other Videos
 
     
     
     

 

Camcorder

 
 
Visitor Sightings
 
           
 

Report a sighting of this fungus.

 
  This button not working for you?
Simply email us at info@MinnesotaSeasons.com.
Be sure to include a location.
 
   

 

 
           
 
MinnesotaSeasons.com Sightings
 
 

 

 

 

 

Binoculars


Last Updated:

About Us | Privacy Policy | Contact Us | © MinnesotaSeasons.com. All rights reserved.