elm bead gall mite

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Aceria is a genus of tiny mites. They are so small that they are almost impossible to see with the naked eye. Unless a scanning electron microscope is available, a morphological description of an adult individual is useless. However, many mites can be easily identified by the shape of the galls they produce and the plant species on which they are found.

Elm bead gall mite is a specialized plant feeder. It is found exclusively on American elm. It produces small, variable, globular, yellowish-green, bead-like galls on the upper surface of the leaves. The galls are solitary – they do not coalesce into larger galls. They occur singly between secondary veins. They have a rough surface and may be covered with hairs.

Tiny, almost microscopic

American elm (Ulmus americana)

Sources

7, 29, 30.