Holly: Green algae

Photo by: B.M. Johnson

Use IPM (Integrated Pest Management) for successful plant problem management.

Biology Green algae grows on the surface only of leaves, twigs, and trunks. Wet, humid weather favors development of these microscopic, moisture-loving, primitive plants. The colonized holly is not harmed unless sufficient algal growth develops on the leaves and interferes with the photosynthetic process. Algal growth can cause plants to appear somewhat dirty or unhealthy. Typically, however, algae is only an aesthetic concern.

Management Options

• Avoid overhead watering or limit it to times when foliage can dry quickly.
• Do not plant in very damp areas or densely shaded sites.
• Space plantings and prune to provide good air circulation and reduce humidity.

Revision Date:5/6/2009

Use as preventative treatments.

If you choose to use a pesticide, some examples of products that are legal in Washington are listed below.

Always read and follow all label directions.


• Bonide Lime Sulfur Spray
• Lilly Miller Polysul Summer & Dormant Spray Conc
• This list may not include all products registered for this use.

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