Botrytis cinerea Pers. ex Fr.
A blossom-end rot was reported on Rome Beauty apples in the Hudson Valley of New York in 1946. Since then the disease has been observed on McIntosh, Delicious, and Cortland in the same area. The disease is also known to occur in certain states in New England.
The causal fungus, Botrytis cinerea, thrives on cool rainy weather and may infect the young sepals after blossom fall if favorable weather persists for 28 to 34 hours.
The term blossom-end rot is unfortunate because the causal fungus does not cause active fruit decay. On McIntosh and most other susceptible varieties, the superficial infection is soon checked by the rapidly growing, resistant young fruits. The infection dies and all that remains is a dry, dark, crusty, blemishlike lesion (see photo). Infection is sometimes more extensive on Delicious than on other varieties. Secondary fungi may invade the lesion and cause active decay.
Unless rain prevents the timely application of modern fungicides, blossom-end rot is of little importance either in the orchard or during marketing. The disease is included for completeness of the handbook and because Botrytis cinerea may, at times, cause serious decay in long-stored apples and pears at 31° to 32 °F storage.
For control of blossom-end rot the recommended spray schedule of the State agricultural extension service or agricultural experiment station should be followed.