130 



Diseases of Economic Plants 



shoots and leaves exhibit a dwarfing, with leaves small and 

 often crimped about the margin ; leaves of nearly normal size 

 but blanched; apparently healthy vines with leaves and fruit 

 shriveling and dying in the summer; fleshy or corky longi- 

 tudinal excrescences on the stem, which in the autumn dry 

 down and become reddish brown and the following spring 

 slough off; the presence of minute black pustules on a dead 



spur, bark, or wood under 

 the bark; small reddish brown 

 spots 3-4 mm. long on the 

 green shoots. 



The disease is conveyed to 

 new tissue by spores from 

 the pycnidia, also probably 

 by pruning tools. It may 

 also enter the older parts 

 through wounds. Cuttings 

 bearing the fungus probably 

 spread the disease. 



Spraying shoots with Bor- 

 deaux mixture when from 

 73^-15 cm. long will reduce 

 infection. Diseased vines should be pulled and burned, or 

 if the root crown be still sound, they may be cut back to 

 near the ground, when the renewal will be healthy. In the 

 spring and summer it is well to mark sick vines for future 

 eradication. Cut off the diseased parts, using tools not 

 used in ordinary pruning. 



Root-rot ^^^ (various fungi) . — • This rot attacks a few 

 roots at first, but eventually reaches all, and results in death 

 of the vine. It is very destructive in Europe and has been 

 noted in several places in the United States. 



The top growths of affected vines show symptoms first; 

 then follows one division after another until a large vine 

 is reduced to the size of a bushel basket, though numer- 

 ous lateral canes may arise, especially near the base of the 

 plant. The leaf color usually remains normal v/ith no dead 



Fig. 67. — Necrosis of the vine. 

 After Reddick. 



