Blotch rot

Blotch rot is a fungal disease caused by Physalospora vaccinii, a pathogen that primarily affects the fruit of berry crops. It is a significant concern for growers, as it leads to considerable yield losses both in the field and during post-harvest storage.

The primary host for this pathogen is the American cranberry (Vaccinium macrocarpon). The fungus targets developing berries, exploiting points of entry such as skin wounds or natural openings to colonize the fruit tissue, which eventually leads to the total breakdown of the berry's internal structure.

Symptoms of the infection typically appear as dark, water-soaked blotches on the berry surface. These lesions expand rapidly, causing the affected fruit to become soft, discolored, and eventually shriveled or mummified. In humid conditions, fungal structures may become visible on the surface of the infected berry.

The development and spread of blotch rot are highly dependent on environmental conditions, particularly high humidity and prolonged periods of wetness. Such conditions favor spore germination and penetration of the berry epidermis. Proper site management is crucial to minimize the prevalence of the disease in commercial fields.

Effective prevention and control measures require an integrated approach to orchard management:

• Maintaining proper spacing to ensure adequate air circulation and rapid drying of the canopy.
• Removing and destroying infected plant debris to reduce the initial inoculum level.
• Applying recommended fungicides during critical growth stages, such as flowering and fruit set.
• Implementing efficient drainage systems to reduce standing water and field humidity.