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Role and Survival of Monilinia fructicola in Blighted Peach Branches. T. B. Sutton, Graduate Assistant, Department of Plant Pathology, North Carolina State University, Raleigh 27607; C. N. Clayton, Professor, Department of Plant Pathology, North Carolina State University, Raleigh 27607. Phytopathology 62:1369-1373. Accepted for publication 5 June 1972. DOI: 10.1094/Phyto-62-1369.

A discolored streak in the xylem of peach branches, with attached rotted fruits or blighted blossoms infected with Monilinia fructicola, extended from the peduncle for as much as 29 cm toward the tip of the branch and 23 cm toward its base. The streak was shown to be a line of gum-filled lacunae and associated discolored xylem located primarily in the springwood of the current season’s growth. Isolations from the discolored tissues in July, 2 to 3 weeks after fruit infection, showed that M. fructicola was present in most cases within 3 cm of the peduncle. By the following February, M. fructicola was recovered principally from the fruit peduncles on which mummies were attached. The presence of M. fructicola in the fruit peduncle in February suggests that the peduncle can serve as an overwintering site. The development of the discolored streak and the subsequent establishment of M. fructicola in peach branches appear to be associated with a failure of an abscission layer to form which permits the infected blossom or fruit to remain attached to the branch. A toxic substance may be involved in the death of the cells which form the abscission layer, as well as the xylem cells.