258 



MANUAL OF FRUIT DISEASES 



trunks. When affected canes are saved for bearing wood, the 

 fungus spreads into the arm. As a rule the mycelium does not 

 extend into the roots. Pycnidia are developed abundantly on 

 affected canes and on green and ripening berries (Fig. 70). 

 They appear on the former early in the spring, and may be found 

 on canes severely infected the previous year or occasionally on 



the current year's growth. The 

 pycnidia mature shortly after the 

 buds burst in the spring, and 

 the pycnospores ooze out in long, 

 reddish yellow coils, each contain- 

 ing several thousand spores. Rain 

 favors this exudation. Perithecia 

 are developed on a stroma beneath 

 the bark, but these bodies do not 

 seem to be important in the life- 

 history of the fungus. They are 

 rarely found, having been reported 

 from but three southern states. 



It has been shown that the 

 transmission of the fungus through 

 nursery-stock is of no little con- 

 sequence. Badly affected cut- 

 tings do not root. Cuttings 

 which show but few lesions will 

 probably make vines which might 



grow for several years without exhibiting marked evidence of 

 the disease. It has been shown further that infections may 

 result from the pruning tools ; in cutting through an affected 

 vine bits of the fungus, which cling to the tools, are deposited 

 in the cut next made on another vine. 

 Control. 



In attempting to control dead-arm the following points 

 should be remembered: 



FIG. 70. Dead-arm ; fruiting 

 bodies of the pathogene. 



