Symptoms
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Symptoms merely on leaves: galls, excrescences , deformation of leaves, filty galls or felty areas on the lower leaf surface varying considerably; sucking damage (punctual discoloratins); rarely on buds, shoots, blossoms and twigs (cankers)
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Impact
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Generally of low impact, sometimes loss of leaves; some species very common (for instance Aceria on leaves of Acer); many species inject substances into the leaves, which induces the production of abnormal structures by the leaves. In the abnormal tissues the gall mites hatch from the eggs deposited there; the felty areas are an effective protection for the young mites against predators (insects). The structures can be mistaken for galls by insects (gall wasps).
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Control
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Generally no measures necessary; to prevent from the optical impairment in economic plant production, acaricides can be used as a control (see Federal Register of Plant Protection).
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Hosts |
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All tree species;
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Affected plant parts
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Leaf;
Shoot/Twig/Branch;
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