Cranberry anthracnose

Cranberry anthracnose is caused by the fungus Colletotrichum acidae, a significant pathogen affecting commercial berry crops. As a necrotrophic fungus, it colonizes host tissues, causing rapid cell death and degradation. The pathogen survives the winter in infected stems and fruit mummies, which serve as the primary inoculum for the next growing season.

The primary host for this fungus is the cultivated cranberry. While the infection can manifest on stems and leaves, the most economically devastating damage occurs on the berries. The fungus infiltrates the fruit tissue, leading to structural breakdown and making the crop unsuitable for either fresh market consumption or processing.

Typical symptoms include the development of water-soaked, sunken spots on the berries, which eventually darken and become necrotic. Under humid conditions, these lesions produce sticky masses of spores (acervuli). Similar lesions can appear on stems, leading to stem dieback. Early detection of these signs is critical for minimizing losses.

Disease development is highly dependent on environmental conditions, particularly high humidity and rainfall. Spores are dispersed through splashing water, irrigation, and contaminated tools. The pathogen thrives in dense canopy environments where air circulation is restricted and moisture remains on the foliage for extended periods, facilitating infection.

Management strategies require a combination of cultural and chemical controls. Growers should prioritize field sanitation by removing diseased plant material and maintaining proper planting density to improve air movement. Fungicide applications, timed with susceptible growth stages and weather forecasts, are essential for effective management and protection of the fruit.