Cereal Leaf Beetle
John Van Duyn, North Carolina State University, Entomology Extension Specialist
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Cereal leaf beetle (Oulema melanopus) colonizes wheat, oats, and other small grains. Beetles infest wheat and other grains in the early spring and often build-up very high populations. The larvae pupate and resulting adults emerge in late-May/early-June from these fields. The adults emerge as the grain crops are maturing and migrate to corn fields to find food. If corn is adjacent to infested small grain plants may become highly infested with the beetles, especially along edges nearest the small grains. Cereal leaf beetles eat the leaf surface tissue on whorl stage plants. Feeding scars appear as long and narrow streaks eaten between leaf veins, usually on the upper surface. If beetle populations are very high, defoliation can reduce yield, although leaf feeding is usually cosmetic. However, damage is often alarming to farmers even if it poses no economic threat. Beetles do not reproduce or remain for a very long time in corn fields and, therefore, damage is a single, short term event that fast growing corn plants soon overcome.
Insecticides are occasionally necessary to prevent serious defoliation to corn fields or portions thereof. To evaluate the need for treatment, two factors must be considered: (1) assessing the % defoliation and (2) determining if beetles are still present in the field at high numbers; is the defoliation going to get worse?. Defoliation estimates should be compared to Table 6-3 to determine potential yield loss. A 5% potential yield loss and a large beetle population will usually justify insecticide treatment (see Scouting for whorl feeding insects).
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Last revised on 1/31/04.
Published by North Carolina Cooperative Extension Service
Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University at Raleigh, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.