FIELD DISEASES 139 



attention. The disease is often worse 

 where green Aphids are very active. In 

 this case the older vines may be affected at 

 any point. Very often, too, the harder 

 vines may escape the disease which attacks 

 the thin blades on each side. Here the af- 

 fected blades become white and dry and 

 break at handling. If not disturbed they 

 become covered with pink pustules or 

 fruits of the parasitic organism. 



The anthracnose, like the "streak," is of 

 great economic importance, \yhen once 

 introduced into a field the disease spreads 

 rapidly, often destroying the entire crop. 

 Unlike "streak," the anthracnose may at- 

 tack young seedlings, a condition some- 

 times found in the greenhouse. In the 

 field, the disease starts about July 1, when 

 the plants are in full bloom and in the 

 prime of beauty. This is also the time 

 when the bitter rot disease of the apple 



