EFFECT OF PROPICONAZOLE ON NECROTROPHIC FUNGI AND YIELD OF BARLEY GENOTYPES DIFFERING IN SUSCEPTIBILITY TO RHYNCHOSPORIUM-SECALIS

Propiconazole was applied to various barley genotypes in field experiments conducted in the barley-growing areas of the Western Cape Province in South Africa during 1989 and 1990. Rhynchosporium secalis was the pathogen noticed most frequently in both years, reaching infection levels of > 60% at the late milk grain stage in unsprayed plots of Clipper and Stirling. In 1989 leaf blotch was reduced and yield was increased significantly in Stirling with one spray of propiconazole at flag-leaf emergence. In 1990 yield increased significantly in both cultivars when two sprays were applied, one at formation of the first node on the main tiller and the second one at flag-leaf emergence. The yield components affected by R. secalis were kernel weight and kernel size. In 1989 spray treatments also increased yields in one genotype resistant to leaf blotch, but susceptible to spot-type net blotch. Common net blotch could be controlled with one spray and spot-type net blotch with two sprays, but control of these two diseases was not clearly related to yield responses in Rhynchosporium-resistant genotypes. Other factors associated with yield increases caused by propiconazole in the absence of recognized foliar diseases are discussed.