There are several species of mites that cause galls on the leaves of maple trees. Maple gall mites are very small, and can only be observed under magnification. The only way that a mite can be identified by a naked eye is by the galls that they produce. Each mite produces a gall with a unique size, colour and shape.
In Greater Sudbury, you're likely to find a few species of gall mite. Crimson perineum mite (Eriophyes regulus) causes red patches on upper or lower surfaces of the leaves of sugar, silver and red maple. Maple gall bladder mite (Vasates quadripedes) causes small, rough growths on the upper surface of the leaves of silver and red maple. Maple spindle gall mite (Vasates aceris-crummena) causes spindle shaped growths on the upper surface the leaves of sugar, silver and red maple.
Maple gall mites are often unsightly, but the health of the tree is not usually affected. The mites overwinter on twigs at the base of the bugs. When spring arrives, the mites crawl onto unfolding leave, infect them, and the gall formation begins.
Apply a dormant oil spray in the spring before buds open, and the temperature is above 20 C. Make sure you talk to a specialist before attempting this method, as some species of maple do not respond well to treatment.
Knowing more about tree health can help people recognize and know the difference between exotic pests and native diseases. Follow our posts here on Northern Life to learn more over the next few weeks.
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Images: University of Kentucky Entomology.
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