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University of Illinois Extension

Bacterial Leaf Spot

Pseudomonas spp. & Xanthomonas spp.


(1 = rare 5 = annual)  


(1 = very little damage 5 = plants killed)  


Heuchera sp. (Coral Bells) & Echinacea sp. (Coneflower) and other plants.    


Pseudomonas causes "reddish" brown spots that may cause the leaf to distort. Xanthomonas causes small brown angular to circular spots with yellow halos. In some plants these bacteria can cause dead spots in foliage and or fruit and sometimes cankers in stems.  

Life Cycle

The bacteria overwinters in dead plant material, but does not survive for long in water or soil. Bacteria are weak pathogens and need a natural opening (stomates and lenticels) or an injury (mechanical, insect or another disease) to infect.


Never work on plants or in the garden while plants are wet since the "bruising" and other mechanical injury helps to spread diseases. Bacteria are not controlled with fungicides. There are no bactericides available to gardeners that control these bacteria. Sanitation is the main control for these leaf spots.

Filed under plants: Flowers

More information is available on Hort Answers.