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Gall-making Mites on Sugar Maple Leaves

S6-2-15 mite-making galls 060Within a week or two of unfurling, Sugar Maple leaves are attacked and consumed by all kinds of creatures, some of which are insects and mites that cause the leaves to develop abnormal growths called galls. Certain species of eriophyid mites form felt, or erineum, galls, often on Silver and Sugar Maple leaves. After spending the winter months under the scales of buds, these mites emerge in the spring when leaves appear, move out onto the surface of the leaves and begin to feed. Their feeding induces the growth of thousands of tightly-packed leaf hairs which provide shelter for the mites on the leaf surface. These hairs appear as bright pink or red patches that resemble felt. The mites, too small to even be seen with a hand lens, move to the inside of these structures for the rest of the growing season.

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6 responses

  1. Kathie Fiveash

    Are these galls actually harmful to the tree? I wonder how much trees/plants lose in resources as they react to the insect/mite/fungus invader. I suppose we would have to call all gall-stimulating organisms parasites.

    June 2, 2015 at 10:40 am

    • Hi Kathie,
      Most galls do not adversely affect plant health as far as I know…

      June 3, 2015 at 9:30 pm

  2. Everything is food! (My motto that helps me overcome garden-muncher anxiety!)

    June 2, 2015 at 10:40 am

  3. It looks to me as though there’s another type of gall, with a wart-like appearance, on the leaf in the photo? Do you know what causes galls like these? I see them sometimes on maple leaves in the Moosehead region.

    June 2, 2015 at 2:36 pm

    • Hi Wendy,
      I don’t see any other type of gall on this leaf…could be my eyesight! Sorry!

      June 3, 2015 at 9:28 pm

    • Charlene Donahue

      THe other galls are maple spindle gall mites, V. aceriscrumena.

      June 15, 2015 at 2:06 pm

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