Apple Disease - Core Rot

Symptoms

Dry core rot is a slow, dry, and corky rot that affects the mesoderm tissue (flesh) surrounding the core. External symptoms are rare, except infected fruit may color and fall prematurely. Wet core rot is a more aggressive wet rot that rapidly develops further during storage and may cause partial or complete fruit rot.

Disease Cycle

Dry rot causal fungi (Alternaria spp.) colonize flower parts during or shortly after bloom. They grow from the flower parts into the open calyx tube and into the core region. Subsequent growth and mesoderm infection are most likely influenced by several physiological and environmental conditions. Disease appears to be favored by mild temperatures and wet weather during bloom, as well as in late summer. Wet core rot infections, caused by Penicillium spp., Fusarium spp., Diplodia seriata, and Botrytis cinerea, can take place within the orchard, as well as during fruit dipping in contaminated water in the packinghouse. Wet core rot infections in packinghouses are influenced by fruit shape and fungal population sizes in dip solutions. Immersion depth and time may also influence the incidence of wet core rot.

Disease Management

Core rots have been controlled with fungicides. Apples riper than normal at harvest may have a high incidence of infection and should not be stored.