Purple Bordered Leaf Spot

(Phyllosticta minima)

Conservation Status
Purple Bordered Leaf Spot
 
  IUCN Red List

not listed

 
  NatureServe

not listed

 
  Minnesota

not listed

 
           
           
           
 
Description
 
 

Phyllosticta minima is a common and widespread fungus. It occurs in eastern North America and west to the Great Plains. It causes a disease known as Purple Bordered Leaf Spot on maples. It infects mostly Amur, Japanese, red, and silver maple, but also mountain and sugar maple, and in other areas, Tartarian and sycamore maple.

Infections are most common in years with a wet spring and early summer. The infection is most severe on the bottom third of the tree, where there is more moisture. Some infected leaves may eventually turn brown and drop off the tree. Rarely, the infection is severe enough to cause partial defoliation in late summer, but most trees are able to withstand the infection.

Infestation first occurs in the spring, when rain and wind causes spores to be splashed and blown onto new leaves. The infected leaf develops small, round, yellowish-green spots (lesions), less than ¼ in diameter. The lesions eventually turn tan and have distinct purple, red, or brown margins. Tiny, black, pimple-like fruiting bodies (pycnidia) form in each lesion and can be seen with a hand lens. The pycnidia are usually arranged in a circle in the middle of the lesions. The dead tissue in the middle of the lesion sometimes breaks away, leaving a small hole.

The pycnidia overwinter in the leaf litter and produce spores the following spring. Control involves removing leaves with spots from the tree, and raking up and removing fallen leaves. That prevents further infections in the current growing season, and reduces the number of infected leaves that will overwinter.

 
     
 

Similar Species

 
  Ocellate gall midge (Acericecis ocellaris) produces a yellow spot with a red border and often a red center on maple leaves. A close look at the underside of the leaf reveals a small maggot in the center of the spot.  
     
 
Habitat and Hosts
 
 

Maples

 
     
 
Biology
 
 

Season

 
 

Spring to fall

 
     
 
Distribution
 
 

Distribution Map

 

Sources

4, 7, 26, 29, 30, 77.

 
         
         
 

Occurrence

 
 

Common

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

Order

Botryosphaeriales  
 

Family

Phyllostictaceae  
 

Genus

Phyllosticta  
       
 

Synonyms

 
 

Phoma minima

Phyllosticta minima var. monspessulani

Phyllosticta monspessulani

Sphaeropsis minima

 
       
 

Common Names

 
 

Bullseye Leaf Spot

Frogeye Leaf Spot

Maple Leaf Spot

Maple Phyllosticta Leaf Spot

Phyllosticta Leaf Spot

Purple Bordered Leaf Spot

 

 

 

 

 

 
 
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