It was aimed to verify the chief leaf diseases that occurs in alfalfa, in Lavras-MG, state of Minas Gerais, of 1997 september to 1998 october. A randomized block trial subplots in time, whose factors were 35 alfalfa cultivars in the plots and 11 evaluation times, which corresponded to the months, in subplots. Evaluations were performed at 28 days after the cut, when ten stems here collected by plots for evaluation of defoliation and determination of severity of the diseases. The data here submitted to the variance analysis and the contrasts among averages compared by Scott-Knott test at 5%. The leaf spot happened during the whole year, with a greatest severity in the periods more colds of the year. The summer black stem and leaf spot, it presented greater severity at the end of summer and beginning of the autumn and the rust reveled a greatest severity in the evaluations of November. The most resistant cultivars to leaf spot, summer black stem and leaf spot and defoliation were Crioula, P 30 and Costera SP INTA. The cultivars MH 15 and MH 4 stood out by larger resistance to the rust.
climatic conditions; cultivars; occurrence; resistance; susceptibility
