The objective of this research was to evaluate the intensity of Alternaria black spot, caused by Alternaria brassicicola and/or Alternaria brassicae, and black rot, caused by Xanthomonas campestris pv. campestris in organic cultivation of brassicas in Pernambuco and Santa Catarina. The survey was carried aut from November 2001 to February 2002, in 103 fields under organic farming systems with different brassicas. High prevalence of the diseases was registered in both states, except on Chinese cabbage in Santa Catarina. Prevalence of Alternaria black spot was 100% on broccoli fields in Pernambuco, as well as on cauliflower in both states, while the black rot reached that level on broccoli and cauliflower fields in Santa Catarina. On the average of the different brassica species, the diseases were more prevalent in Pernambuco than in Santa Catarina. However, when the severity averages of each disease were considered, no significant differences were observed between the two states, although the climatic conditions were highly different. The Alternaria black spot severity varied among the brassica species in Pernambuco, being lower on kale. In Santa Catarina no significant differences were observed among the brassicas species. In relation to the black rot, only in Santa Catarina was there a difference in the disease severity, with the lowest level on Chinese cabbage. No significant correlations were observed either between severity levels of Alternaria black spot and black rot, neither between disease severity and total number of plants or plant age.
Alternaria brassicicola; Alternaria brassicae; Xanthomonas campestris pv. campestris; severity; prevalence
