EFFECTS OF SEED AND FOLIAR FUNGICIDES ON PROGRESS OF NET BLOTCH AND YIELD IN BARLEY

Abstract

Effects of systemic fungicides on progress of net blotch, caused by Pyrenophora teres, were examined in field plots. Disease intensities and apparent infection rates (r values) in barley grown from carbathiin-treated seeds were similar to those of the checks 29–30 days and later. Etaconazole used as a seed treatment reduced disease intensities for about 29–42 days, but r values later accelerated and exceeded those of the checks. Propiconazole applied to the foliage at early tillering reduced r for about 12 days, but disease subsequently progressed more rapidly than in the checks. Applications of propiconazole at spike emergence reduced r for 13–15 days. According to the observed r values and disease intensities, the following temporal relationships of fungicide applications and disease progress were recognized: (1) period of reduced epidemic rates; (2) period of accelerated epidemic rates; (3) period of epidemiologic impact of the fungicide (the summation of 1 and 2). Seed treatments and tillering sprays failed to increase barley yields significantly. However, when propiconazole was applied at spike emergence, or at both tillering and spike emergence, 1000-kernel weights increased by 17.3% and 17.8%, respectively, at one location, and grain yields by 14.2% and 19.1% at a second location.Key words: Etaconazole, propiconazole, carbathiin, epidemiology, Pyrenophora teres, Drechslera teres