Purple Bordered Leaf Spot

(Phyllosticta minima)

               
Conservation Status

IUCN Red List

not listed

Purple Bordered Leaf Spot

NatureServe

not listed

Minnesota

not listed

Occurrence

Common

Season

Spring to fall

Habitat/Hosts

Maples (Acer spp.)

 
Identification

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.

 
Distribution Distribution Map  

Sources: 7, 26, 29, 30, 77.

 
Comments

 

 
Taxonomy

Division:

Ascomycota (sac fungi)

 

No Rank:

saccharomyceta

 

Subdivision:

Pezizomycotina

 

No Rank:

leotiomyceta

 

No Rank:

dothideomyceta

 

Class:

Dothideomycetes

  No Rank:

Dothideomycetes incertae sedis

 

Order:

Botryosphaeriales

 

Family:

Phyllostictaceae

 
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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