258 MANUAL OF FRUIT DISEASES 
trunks. When affected canes are saved for bearing wood, the 
fungus spreads into the arm. Asa rule the mycelium does not 
extend into the roots. Pyenidia 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 pyenospores 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- 
m | sequence. Badly affected cut- 
Fic. 70.— Dead-arm; fruiting tings do not root. Cuttings 
bodies of the pathogene. 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 : 
