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Cereal Leaf Beetle

Oulema melanopus (L.)

Description: Adults are about 1/4" long. They have metallic blue-black heads and wing covers. The area behind the head (thorax) is reddish-brown and the legs are yellow-brown. Larvae (up to 1/4" long) are yellow, but usually have a brown or black coating of fecal material that gives them a slimy, wet appearance. The oblong eggs (about 1/16") are yellow to orange and usually laid singly on the upper leaf surface.

Biology: There is only one generation a year. Most adults emerge in March from overwintering sites in field debris, bark crevices, and other shelter. After mating the females lay up to 400 eggs individually on the upper leaf surface of preferred hosts such as wheat, oats, and barley. Eggs take 4 - 23 days to hatch depending on temperature. The larvae feed for up to three weeks as they pass through four development stages. Both the adults and larvae feed on small grain leaves by chewing between the leaf veins. The adults eat all the way through, but the larvae feed on the upper leaf layers. Larval feeding injury gives small grain leaves a bleached, white appearance. Most damage occurs in April from the last larval stage. The larvae then pupate in the soil for 12 - 25 days. Adults emerge and often feed on corn in June before flying to shelter where they remain relatively inactive. The feeding injury to corn is not considered economic.

Management: The treatment threshold is 50 larvae per 100 stems (0.5 larvae/stem). Check 10 stems in 10 representative areas of a field. Keep in mind that cereal leaf beetle damage is seldom uniform across a field and usually highest at field margins. The greatest yield loss occurs from defoliation before or during early kernel formation. See the most recent issue of the Ag. Chemical Handbook for control recommendations.

Reference: Hunt, T. N. and J. R. Baker. 1982. Insect and related pests of field crops. AG-271 North Carolina Agricultural Extension Service. 214 pp.

Prepared by Jay W. Chapin, Extension Entomologist/Professor,  Department of Entomology, Soils, and Plant Sciences, Clemson University, Edisto Research & Education Center

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