Razionalizzazione della difesa del riso da elmintosporiosi e brusone

Epidemics of rice brown spot and rice blast were monitored for several years on different cultivars. We evaluated the efficacy of known and new fungicides applied at different doses and with different strategies based on rice phenology and diseases epidemiology. Leaf brown spot generally preceded leaf blast. At maturity, disease severity on flag leaf seldom exceeded 10-15%. Panicle blast incidence reached 100% between grain set and milk ripeness growth stages, but severity hardly exceeded 5%. Fungicides efficacy against Cochliobolus miyabeanus (S. Ito & Kurib.) Drechsler ex Dastur on leaves varied considerably among products, years, and application strategies and it was comprised between 6 and 67%. The best results were obtained with two treatments of azoxystrobin or a tank-mix of fenbuconazole and tricyclazole or iprodione and tricyclazole applied between booting and flowering growth stages. The same fungicides gave good protection against panicle blast. The two-treatment phenological strategy was not always better than one-treatment phenological strategy.