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Algal Leaf Spot Description:

Raised, wavy, cushion-like spots are symptoms of algal leaf spot, also known as green scurf. The spots are greenish, pinkish or grayish and less than 1 cm. in diameter. They may encircle a twig, creating a girdling canker.

Hosts:

Plants weakened by other stress factors are the most susceptible to infection and further weakening from this disease. It affects magnolia, camellia, holly, and many other plants.

Biology and Symptoms:

Algal leaf spot is caused by the alga (plural, algae) Cephaleuros. Thick-leafed plants are infected in the summer, when rain spreads the pathogen. Colonies can survive on fallen leaves for a time and spread to growing leaves. After the initial infection, secondary reproduction or spread occurs over an 8- to 9-month period.

Management:

This disease primarily causes damage to the appearance of plants. Otherwise, the impact is usually minimal. When new growth is expanding, make two applications of an approved algaecide, spaced 4 weeks apart. Collect and discard infected, fallen leaves to help reduce the spread of the disease. If the infestation is limited, selectively remove infected leaves from the plant.

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