Cultivar Differences in Response to Triadimenol Seed Treatment for Control of Barley Net Blotch Caused by Pyrenophora teres. J. Edmund Sheridan, Plant Pathologist, Botany Department, Victoria University of Wellington, Wellington, New Zealand. Nick Grbavac, Graduate Research Assistant, Botany Department, Victoria University of Wellington, Wellington, New Zealand. Plant Dis. 69:77-80. Accepted for publication 29 June 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-77.

In the spring of 1981, there was an upsurge of net blotch, caused by Pyrenophora teres, in commercial barley crops in the North Island of New Zealand. In the following season, net blotch became epidemic in the Manawatu/Wanganui districts. This was believed to be due to the failure of the popular seed treatment containing triadimenol + fuberidazole to control the disease on the newly introduced cultivars Mata and Triumph. Trials confirmed the poor performance of triadimenol on these and other new cultivars and its continued effectiveness on the older cultivar Zephyr. In the autumn of 1984, triadimenol also failed to control net blotch on Zephyr. The problem appears to have arisen from the introduction of a triadimenol-insensitive fungus on overseas cultivars.