This disease was formerly confused with scald. As stated elsewhere, scald has been used broadly to indicate what is now known to be several distinct diseases. Rot was then included under the term scald.
Next to scald, cranberry rot is the most important fungous disease of this fruit. It is found commonly in New Jersey, and is reported from West Virginia, Massachusetts, Wisconsin and Nova Scotia.
The basis for the confusion of rot and scald is their close resemblance. The two diseases do look very much alike, both externally and internally. The first external sign of the cranberry rot disease is that of a small, light - colored soft spot on the berry. The whole berry is finally destroyed. Dark, concentric rings, as described for scald, sometimes appear as a character of the lesion.
The causal pathogene is the fungus Acanthorhynchus Vaccinii. It hibernates in the fallen leaves and fruits. In the spring ascospores are forcibly discharged from asci in the perithecia. The spores are gelatinous and thus adhere to any object with which they come in contact. It is not known just when this discharge occurs, but probably soon after the water is removed from the bog in the spring.
The ascospores germinate in damp air or in water, producing a short germtube, which is terminated by a peculiar, dark-colored, disc - like body, an appressorium, with a lobed margin. The small projections at the margin firmly attach the appressorium to the leaf by dissolving small cavities in the epidermis. From the center of the appressorium arises another germtube, which enters the leaf usually through a stoma. This whole process probably takes place in a few hours. The mode of entrance into fruits has not been determined.
The treatment as outlined for scald gives satisfactory control for the rot disease (page 195).
Shear, C. L. Cranberry diseases. Rot. U. S. Agr. Dept. Plant Indus. Bur. Bul. 110: 26 - 30. 1907. Shear, C. L. Fungous diseases of the cranberry. Cranberry rot.
U. S. Agr. Dept. Farmers' Bul. 221: 7 - 8. 1905.