VIEW ARTICLE

The Influence of the Retention of Immature Apple Mummies by Certain Cultivars on the Overwintering of Physalospora obtusa. J. Holmes, Graduate Assistant New Hampshire Agricultural Experiment Station, Department of Botany, University of New Hampshire, Durham 03824; A. E. Rich, Plant Pathologist, New Hampshire Agricultural Experiment Station, Department of Botany, University of New Hampshire, Durham 03824. Phytopathology 60:452-453. Accepted for publication 6 October 1969. DOI: 10.1094/Phyto-60-452.

Frogeye leaf spot development was associated with immature apple mummies on the Cortland variety in New Hampshire. About 83% of immature apple mummies were infected with the causal fungus Physalospora obtusa. Large numbers of immature apple mummies (retained June drops), but relatively few mature apple mummies, remained over winter on Cortland trees. Mummies were not retained on McIntosh or Red Delicious varieties. Increased inoculum in the form of immature mummies from Cortlands was shown to increase the incidence of frogeye leaf spot in McIntosh and Red Delicious. Retention of June drops by some apple varieties appears to be of primary importance in the overwintering of the organism, and is largely responsible for the varietal differences in the amount of frogeye leaf spot and apple rot observed.