414 MANUAL OF FRUIT DISEASES 



the cluster. The fungus evidently hibernates as pycnospores 

 in pycnidia; in the spring these spores ooze out on the bark. 

 Dead and decaying canes are sources of the inoculum. It has 

 been shown that the fungus may live as long as four years on 

 fallen dead canes. It is believed that the pathogene is carried 

 in the soil particles on nursery-stock. Furthermore, the prac- 

 tice of laying down and covering of canes with soil in the fall to 

 protect them from winter-injury, is thought to spread the or- 

 ganism. A perithecial stage has been discovered, but its role 

 is unknown. 



It is peculiar that the fungus may cause most serious damage 

 in dry seasons. This is explained on the grounds that canes 

 become infected during the first season of their growth, but 

 do not show effects until the following year. Weather condi- 

 tions have a positive influence on inoculation and incubation, 

 but not on the growth of the fungus in the cane. 



Control. 



No definitely established remedial measures are at hand. 

 Ordinarily plantations may be expected to recover, even if 

 badly diseased for one year. As a precautionary measure, 

 plants should not be selected from nurseries in which the cane- 

 blight is present to any great extent. Since the fungus may 

 live on fallen canes for four years, it is inadvisable to replant 

 on soil within this time after a severe attack. In any case the 

 old canes should be burned. Dead and diseased canes should 

 be removed soon after the fruiting-season, and again in the 

 early spring. If the disease is particularly troublesome, look 

 for any wild blackberries and wild red raspberries in the vicinity 

 of the plantation. Their destruction is one step toward elimi- 

 nating the fungus. 



According to present knowledge, the application of fungicides 

 is not promising. In some cases bordeaux mixture has been 

 applied as follows : (1) when the canes are a few inches high ; 

 (2) subsequently at intervals of two weeks until the middle of 



