The cereal leaf beetle (CLB), Oulema melanopus (L.) (Coleoptera: Chrysomelidae), an introduced pest of small grains, causes considerable damage and yield reduction in wheat, oat and barley crops in North Carolina. Adults and larvae feed on the foliage, reducing the ability of the plant to form grain heads. CLB is found in all grain growing areas of the state, from the coastal plain to the western piedmont. Adult beetles are about 3/16 inch (5mm) long with metallic steel-blue wing covers and a red thorax. After overwintering in leaf litter near the fields, adults emerge in the spring to feed, mate and lay eggs. Small, yellow, oblong eggs are laid individually on the upper surface of leaves, and are usually present from mid-April to early May. Larvae are yellow and grub-like, and cover their bodies with a slimy brown defensive substance that is a mixture of mucus and fecal matter. Peak larval populations occur in early-May. Larvae drop to the soil to pupate in earthen cells in the upper few inches of soil, and by mid to late May, adults emerge to feed on grasses such as fescue or corn before moving to aestivation sites.
Cereal leaf beetle was first detected in North Carolina in 1977. In 1978, in cooperation with USDA, the NCDA&CS' Biological Control Program began releasing parasitic wasps into small grain fields along the Virginia border and in the piedmont. Biological control of the CLB previously had been implemented by USDA and cooperating agencies in the upper midwest of the United States and in Canada, and the program was successful in managing populations of the pest. A total of 3 species of larval parasitoids and one egg parasitoid were released in those regions.
Courtesy of the USDA Niles Laboratory
The egg parasitoid, Anaphes flavipes (Foerster) (Hymenoptera: Mymaridae), is a minute wasp which lays its eggs inside the eggs of the CLB. One or two wasps will emerge from each successfully parasitized egg. Although this insect is usually present after the peak CLB egg populations, up to 5 generations of wasps may occur each year. From the initial introductions, A. flavipes has spread to most of the grain producing regions of the state. Because it has the ability to disperse well on its own, it is not being reared for redistribution.
Courtesy of the USDA Niles Laboratory
A field nursery or insectary was started at the Piedmont Research Station near Salisbury, NC, in 1987 to rear Tetrastichus julis (Walker) (Hymenoptera: Eulophidae), a gregarious larval parasitoid. This parasitic wasp usually attacks larvae in the second and third instar. CLB larvae remain on the host plants, then pupate in the soil. After the pupal cell is formed, the hymenopteran completes development, and some of the T. julis diapause until the following spring, but some emerge in late May. Between 1989 and 1991, almost 30,000 parasitoids in the form of parasitized larvae were redistributed to growers for release in their own fields. Additional insectaries have been established at Oxford Research Station in Granville County and the Tidewater Research Station in Washington County. Cooperative efforts with USDA include the introduction into the insectaries of parasitoids from various regions of Europe to find strains which are best suited to the climate of North Carolina. After these become established and increase in numbers they will be available for redistribution.