Severity of alternaria in sunflower crop in the Cerrado region of Federal District, Brazil

Abstract

Severity of alternaria leaf spot was evaluated in five genotypes of sunflower as a result of two densities of population and two sowing dates. The experiments were conducted in the Embrapa-Centro de Pesquisa Agropecuária dos Cerrados experimental field, at Planaltina, DF, Brazil, on the crop season of 1998/1999 on an Oxisol soil. The experimental design was in randomized blocks in a 5 x 2 factorial with three replicates. The percentage of infected plants was estimated based on weekly observations considering scores from 0 to 5 in lower, middle and upper parts of the plant. The occurrence of alternaria was not influenced by density of population of 42,000 or 49,000 plants/ha. All cultivars were susceptible to the disease. The climatic conditions for each sowing date changed the disease severity.