Various instances of algal stem blotch on blueberry have been reported in Georgia in recent days, according to the University of Georgia Blueberry Blog.
Growers should be aware that since the disease is caused by an alga rather than a fungus, it is highly unlikely that fungicides will be an effective management option. University of Florida recommendations suggest that sprays with copper-containing fungicides can reduce algal sporulation and protect healthy canes from infection.
But these products will not eradicate the disease or eliminate any existing symptoms.
The disease’s development is attributed to favorable weather conditions of rain and warm temperatures. While the disease does not have a strong history in Georgia, it was reported in multiple locations two years ago.
Georgia farmers should familiarize themselves with the disease symptoms since it has been observed in two out of the last three years. Producers should contact their local Extension agent if they require further information regarding the disease diagnosis and management moving forward.
The disease causes red blotches that appear on the young stems of blueberry plants. As infected stems grow older and become woody, the lesions may be less obvious until the alga sporulates through the bark, forming felt-like mats of bright orange sporangiophores.
The other noticeable symptom on infected stems is chlorosis or bleaching of leaves.