Surveys of the intensity of cercospora leaf spot of lettuce caused by Cercospora longissima were performed in 25 conventional and 25 organic farming areas in 2 planting periods, January-April (I) and June-September (II) 2002, in State of Pernambuco (Brazil). Disease prevalence was high (> 88%) in all evaluated situations. Disease severity ranged from 0.0 to 16.9% in conventional farming areas and from 0.0 to 22.5% in organic farming areas. In both systems, disease severity was significantly higher in period I when precipitation was almost 3 times higher to that in period II. However, only in period II, significant differences in disease severity were found between farming systems, with high values in the organic system. There were no significant correlations among disease severity levels in the areas in both evaluated periods inside each farming system.
Cercospora longissima; Lactuca sativa; disease assessment