Bean Diseases 



113 



covered with sunken brown to black specks. These 

 are especially evident on the white seeded varieties. 

 In severe attacks, the seeds are covered with deep 

 sunken black spots (fig. 15, c.) which are rifted in 

 the center. On the leaves the disease attacks the 

 veins, which become blackened and somewhat 

 shrunken. Frequently it attacks the petioles, espe- 

 cially at the point of leaf attachment. In this case, 

 the foliage drops off, leaving the bare petioles or 

 stems. Anthracnose on the pods begins as small, 

 circular, pin-point, dark red spots which enlarge, 

 and later elongate into maroon colored pits, cracks, 

 or cankers (fig. 15, a.). On young seedlings the 

 stem rots off a short distance above groimd. 



The Organism, Spores are formed on the spots 

 or cankers of all parts affected (fig. 15, b.). These 

 are imbedded in a gelatinous substance and may be- 

 come loosened only by water splashing upon it. It 

 is at this stage that the disease becomes serious, for 

 it is then spread from plant to plant. When the 

 spores are lodged on a new bean plant or on a new 

 part of the same plant, infection takes place through 

 the penetration of the tube of the germinated spores. 



Control. Spraying has not given satisfactory re- 

 sults. The best control is to plant clean seed select- 

 ed from clean pods. The latter, before shelling, may 

 be dipped for ten minutes in a solution of one part 

 of corrosive sublimate to a thousand of water. The 

 treated pods are then dried in the sun, shelled, and 

 the seed put away in dry Mason jars until planting 

 time. Should weevils threaten these seeds, they 



