CRANBERRY DISEASES 201 



ROT 

 Caused by Acanthorhynchus Vaccinii Shear 



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. 



Symptoms. 



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. 



Cause. 



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-col- 

 ored, disc-like body, an appressorium, with a lobed margin. 

 The small projections at the margin firmly attach the appres- 

 sorium 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 



