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Elm Flea Weevil

May 11, 2005

Elm flea weevil is numerous in northeastern Illinois, feeding on a variety of elm species. Identification is uncertain, but appears likely to be Rhynchaenus alni, known in Europe as the elm leaf-mining weevil. Damage appears as numerous pinhead-sized holes in leaves. Close observation reveals tiny beetles about 1/16 inch long, primarily on the lower sides of the leaves. They are reddish insects with black heads and black spots on the wing covers. Like grasshoppers, they also have thickened hind legs that they use to jump, and then they fly when disturbed.

Many of them will be mating pairs. These insects lay eggs into the leaf midvein. The hatching larva create a blotch mine at the leaf tip. Refer to the German Web site http://www.bladmineerders.nl/minersf/coleopteramin/rhynchaenus/minrhynalni_f/minrhynalni.htm for a photo of the likely damage.

Control the flea weevil adults with a spray of acephate (Orthene), imidacloprid (Merit), bifenthrin (Talstar), or carbaryl (Sevin). The Orthene and Merit should also prevent the larval mines from appearing later.

Author: Phil Nixon Morton Arboretum


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