Effect of Cereal Leaf Beetle on the Yields of Resistant and Susceptible Winter Wheat¹

Abstract

Field tests were conducted with l0 winter wheat ( Triticum aestirum L. em. Thell.) genotypes to determine the effectiveness of cereal leaf beetle (CLB), Oulema melanopus (L.), resistant wheat reducing larval densities and yield losses. Yield loss data were obtained by comparing yields of insecticide‐treated plots with CLB infested plots. The test included a cereal leaf beetle resistant cultivar, ‘Downy’, and three other resistant genotypes. All four resistant entries had pubescent leaf surfaces. Larval densities and larval feeding damage were lower on pubescent‐leaved entries than on wheat lines without high levels of leaf surface pubescence. In 1978 there was no grain yield reduction in three resistant entries, while the yield loss of susceptible lines ranged from 17.6 to 25.6%. Larval density on these cultivars ranged from 4.3 to 10.4 larvae per stem. Kernel weight was the most sensitive yield component in this test, with significant reductions in four of the six susceptible cultivars. Winter wheat breeders in localities where the CLB has been a problem should at least maintain resistant germplasm even though parasitoids have been established in many areas for biological control of the CLB.