Cultural characteristics and pathogenicity of Melanconium juglandinum

Cultural characteristics and pathogenicity of Melanconium juglandinum, the agent of the black pustular dieback of Juglans spp. in Europe were investig ated. Melanconium juglandinum was consistently isolated from diseased twigs and branches of Persian (English) walnut trees (Juglans regia) in Central Italian Apennine valleys. In growth and conidia germination tests, the fung us was shown to be active within a broad range of temperatures (5-30 degree s C), with the optimum being between 20 and 30 degrees C. Monthly artificia l inoculations performed over a period of 2 years with mycelial plugs on 2- year-old seedlings of Persian (English) walnut developed symptoms within 15 days with maximum canker length occurring when inoculation was carried out between June and August. Koch's postulates were fulfilled and M. juglandin um was proved to be a virulent pathogen.