Tree fruit scientists spoke about recent research on bitter rot and apple replant disease on Tuesday during the Mid-Atlantic Fruit and Vegetable Convention.
Bitter rot causes sunken lesions in apples and produces orange spores. At least eight species of fungus cause bitter rot, but they are closely related, produce identical symptoms and can be managed essentially the same way, said Phillip Martin, a Penn State doctoral student.
Bitter rot has been increasing in recent years, thanks in large part to the expanding acreage of Honeycrisp. Popular with consumers, the variety is also highly susceptible to bitter rot fungi.
Bitter rot grows best in long periods of wetness between 70 and 80 degrees. The fungus often infects the fruit and stays dormant until late in the season or even after harvest.