Cereal leaf beetle
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| iCereal Leaf Beetle | ||||||||||||||||||||
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| Oulema melanopus (L., 1758) |
The cereal leaf beetle (Oulema melanopus) is an agricultural pest and biological control success story. The beetle is mostly blue-black in color, with an area of deep red just behind the head. The legs are dull orange. The most common host plants of the cereal leaf beetle are barley, oats, and wheat, but they are also found on rye, millet, rice, many types of wild grasses, and new corn shoots. The beetle has a history as a major crop pest in Europe, Asia, and parts of north Africa, but serious eradication efforts did not begin until the pest began to destroy oat fields in the United States in the 1960s. Insecticides were used without success, but when natural enemies of the beetle were discovered, imported, and released in affected fields, the cereal leaf beetle came under control.
The cereal leaf beetle overwinters in fields of wild grasses, and as the weather warms in the spring it enters cultivated fields and deposits eggs. The larvae emerge and cover themselves with their own excreta in order to mimic the droppings of birds or other insects. They usually appear as shiny, wet lumps adhered to the surface of leaves. They gorge on the plants, then drop off and pupate in the soil for about 3 weeks, emerging full-grown to continue feeding on the plants. Both adult and larva prefer young plant shoots or areas of new growth on established plants. Damage from cereal leaf beetle is apparent when the tips of leaves turn white and the leaves develop white stripes or slits where the beetle has consumed a strip. A field with extensive damage will look frosted or whitewashed.
Parasitoids successfully employed against the cereal leaf beetle as agents of biological control include the parasitic wasps Diaparrsis carinifer, Lemophagus curtus, and Tatrastichus julis, which attack larvae, and Anaphes flavipes, which is an egg parasitoid. Lady beetles eat the eggs and larvae.
