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Leaf-Eating Beetles in Michigan

Beetles are an important part of the environment in Michigan and are often beneficial. Sometimes beetles do damage to crops and forests, especially when they were not meant to be in the area and have no natural predators to control them. Michigan has several species of native beetles, and it has species that were introduced accidentally or purposely to control unwanted species of plants.

  1. Plant-Specific Beetles

    • Many beetles in Michigan are plant specific; most are named after the plant they prefer, such as the dogbane leaf beetle, which feeds on the dogbane plant and which lives in Michigan and other states. The beetles mate and lay eggs on the plant, and the young, when they hatch, fall to the ground and burrow to eat the roots. When they become adults, they devour the leaves of the plants. The dogbane leaf beetle is metallic green and has coppery hues that distinguish it from other beetles.

    Introduced Beetles

    • In an effort to eradicate exotic plant species, forestry and agriculture officials in Michigan have introduced specific beetles. They released two leaf-eating beetles, Galerucella pusilla and G. calmariensis, in Michigan to rid the state of purple loosestrife. Before their release the beetles were studied to determine that they rejected nontarget plants that were beneficial to Michigan. In 1996 the beetles were released in 21 states including Michigan. But they had already been released in the Saginaw Bay Watershed in Michigan in 1994 to control swamp loosestrife.

    Crop-Specific Beetles

    • Michigan grows several types of crops, and some, such as cereal and soy, are attacked by crop-specific beetles. The cereal leaf beetle was found near Galien, Michigan, in 1962 and has now spread across United States and is found in wheat-producing states. Cereal leaf beetle was initially an important defoliator in wheat and oats, but as a pest it is now relatively uncommon in Michigan. The bean leaf beetle attacks soy in Michigan. To control species that destroy crops, officials in Michigan have released parasitoids, which are natural enemies, to control them.

    Imported Beetles

    • Beetles not native to a state are sometimes brought in accidentally and do damage. The imported willow leaf beetle has infested trees in the state and caused damage. Both the adult and its larvae feed on the willow leaf and strip the tissue between the veins. The damage is usually not fatal to well-established trees, but an infestation can leave the tree looking brown and unsightly. The beetle does have natural parasitic enemies in Michigan, but some plant owners use insecticides registered for use on the willow leaf beetle.

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