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Bulletin 395 



Frequently in the latter case the spots anastomose. Since the lesions 

 are very small, about one to two millimeters in diameter, the foliage 

 is not injured to any extent by the anthracnose, although later in the season 

 the affected leaves may become more or less ragged. It has been observed 

 also that in some cases the spots drop out and give the shothole effect 

 characteristic of many leaf spots. 



The common leaf spot of the raspberry, which may be confused with 

 anthracnose, is caused by a species of Septoria. The lesion differs from 

 that of the anthracnose disease in being irregular in outline and pale 

 brown in color, with minute pycnidia just visible to the eye. In the 

 case of the Septoria disease a yellowing and dying of the leaves occurs. 



ETIOLOGY 



The anthracnose disease of the raspberry is caused by the fungous 

 pathogene Plectodiscella veneia Burkliolder. 



MORPHOLOGY 



The mycelium of Plectodiscella veneta when mature is hyaline and com- 

 posed of minute cells many of which are globose. In all stages the fungus 



Fig. 15. AscocARP of plectodiscella veneta 



Longitudinal section through the ascocarp, showing various stages in the development of 

 the ascospores. Outlined with camera lucida from prepared slide. The tissue is somewhat 

 shrunken. X 850 



is very local and forms a stroma in the epidermal and subepidennal cells 

 of the host. This stroma is frequently subcuticular, but never has it been 



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