Diseases of sunflower (Helianthus annuus L.) in Viamão and Santo Augusto, Rio Grande do Sul.
Sunflower cultivars growing in Viamáo and Santo Augusto, Brazil, in 1986 were assessed for resistance to rust (Puccinia helianthi), bacterial spot (Pseudomonas syringae pv. helianthi), black spot (Alternaria helianthi) and downy mildew (Plasmopara halstedii) under field conditions. Low severity was recorded for rust, bacterial spot and black spot, while the incidence of downy mildew was high in Santo Augusto. Contisol was the most susceptible cultivar to downy mildew. The hybrids Arbung G-133 and Arbung P-113 were free from infection.