Sclerotinia Rot of Pears in Oregon. R. A. Spotts, Mid-Columbia Agricultural Research and Extension Center, Oregon State University, Hood River 97031. L. A. Cervantes, Mid-Columbia Agricultural Research and Extension Center, Oregon State University, Hood River 97031. Plant Dis. 80:1262-1264. Accepted for publication 12 August 1996. Copy right 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-1262.

Record rainfall occurred in the Hood River Valley during spring of 1993. In late spring, lesions up to 2 cm in diameter were observed on d’Anjou pear fruitlets on the calyx end or where senescent flower parts adhered to the fruits. Sclerotinia sclerotiorum was consistently isolated from infected tissue. Koch’s postulates were tested, and S. sclerotiorum was confirmed as the cause of the disease. Mycelial growth of the pathogen on acidified potato dextrose agar was optimum at 20°C, and the average growth rate was about 10 mm per day. Five pear cultivars were ranked in order of increasing resistance to Sclerotinia rot as follows: d’Anjou, Bosc, Columbia Red d’Anjou, Bartlett, and Cornice. Among eight fungicides tested, only iprodione provided good control of fruit infection.