Disease Note

Calyx End Rot (Sclerotinia sclerotiorum) of Apples in Washington. R. P. Covey, Washington State University, Tree Fruit Research Center, Wenatchee 98801. Plant Dis. 69:726. Accepted for publication 17 April 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-726a.

Calyx end rot of apples (Malus domestica Borkh.) has been observed on cv. Delicious fruit in a number of orchards in central Washington each year since 1982. Only a limited number of fruit have been infected, and infection has never been observed prior to August, at which time the diseased tissue surrounding the calyx becomes sunken, light to walnut brown, and firm and leathery. The lesions seldom exceed 2 cm in diameter. Isolations from infected fruit produced cultures of Sclerotinia sclerotiorum (Lib.) dBy. No sclerotia were observed on infected fruit in moist chambers, and lesions enlarged only slightly. Laboratory inoculation of cvs. Delicious. Rome Beauty, Winesap, and Golden Delicious fruit (about 6 wk before harvest date) with mycelial homogenates resulted in typical lesions, from which the pathogen was reisolated. This is believed to be the first report of calyx end rot of apples in Washington State.