FUNGICIDAL DISEASE SUPPRESSION AND YIELD LOSSES ASSOCIATED WITH SUNFLOWER RUST IN ISRAEL

The effects of rust on the yield components and harvested achene yield of a non-oilseed sunflower cultivar were examined in two field trials in Israel. Head area and the number of achenes per head were decreased during severe rust epidemics, but were unaffected by moderate or mild epidemics. Individual achene weight and the frequency of fertile achenes were influenced by the disease, in relation to its intensity. The fungicide tebuconazole, applied at a rate of 0.125 kg a.i. ha-1, arrested rust development for at least 14 days. Highly significant effects were obtained by spraying when anthesis had occurred only in the outer quarter of the inflorescence radius, whereas the effects of spraying when anthesis was completed were negligible. Differences in yield (0.86-1.15 t ha-1) and in net profit (US$696-1153 ha-1) between sprayed and unsprayed plots were significant (p < 0.05).