One of our most interesting finds this past season was Cephaleuros virescens on an Indian Hawthorn plant near a blackberry farm in Leesburg, GA. You may be wondering why an ornamental disease is a significant find for crop production.
Orange Cane Blotch or Orange Felt (Cephaleuros virescens) is a blackberry disease picking up interest for southeast growers. This plant parasitic green algae is prevalent on blackberries when conditions are hot and humid. Although it is considered a subcuticular parasite, damage has been observed as deep as the cortex region increasing the chances of plant girdling. C. virescens also renders blackberry plants susceptible to secondary infections through cracks in the canes.
The color of these circular blotch lesions ranges from yellow to orange which can easily be confused with blackberry rusts. The felt-like appearance is due to the mass of sporangiophores present on the leaf surface. Active sporulation seen below reveals the zoospores which contain special propeller-like structures used for mobility through actively flowing water. (Think of rain drops running down a plant or rain splashing.) C. virescens has the broadest host range out of the Cephaleuros genus and is also the causal organism for Algal Stem Blotch in blueberries.
For more information on Orange Cane Blotch: https://extension.uga.edu/publications/detail.html?number=C892&title=Orange%20Felt%20(Orange%20Cane%20Blotch)%20of%20Blackberry
For more information on Algal Stem Blotch: https://site.caes.uga.edu/blueberry/2021/09/algal-stem-blotch-on-blueberry/
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