CURRANT DISEASES 211 



of transition from active elongation-growth to that of the 

 maturation-stages. Within a week or two after the spores 

 of the fungus are deposited upon the currant, signs of dis- 

 ease appear. The bark, wood and pith are invaded by the 

 mycelium. Sometimes the leaves also are attacked. The 

 mycelium may be observed in the pith as a fine, whitish, 

 webby growth. 



Shortly after early infection occurs, the fungus forms a simple 

 spore-stage on the withering tips. This is known to patholo- 

 gists as the Macrophoma-form. Following the development 

 of this stage, from midsummer to autumn, a stromatic form 

 appears ; this is called the Dothiorella-stage. This form shows 

 as small, globose, sclerotic bodies on the shoots which have 

 been killed in the earlier part of the season. Toward the end 

 of the summer the stromata of the second or Dothiorella-type, 

 instead of forming pycnidia, develop perithecia. In this condi- 

 tion the fungus passes the winter. The following May and 

 June pycnospores are formed. They are discharged the latter 

 part of June or in early July. At the same time ascospores 

 develop within the perithecia already mentioned. Thus 

 pycnidia and perithecia may be found on old dead canes to- 

 gether. 



Control. 



At the present time there is no method of treatment for 

 currant cane-blight which can be confidently recommended. 

 It has been shown that summer pruning, that is, the syste- 

 matic removal of all diseased canes at frequent intervals 

 during the spring and summer, is of no value so far as the 

 control of cane-blight is concerned. Winter pruning is also 

 inefficient, owing to the difficulty of recognizing affected canes 

 while the plants are devoid of foliage. The careless piling 

 of pruned canes along fences should be avoided. Such brush 

 should be burned before the end of May, in order to destroy 

 the fungus. 



