VEGETABLE AND FIELD CROPS 239 



Stem anthracnose {Vermicularia Dematium (Pers.) Ft.). — 

 Numerous black scars appear on the stems a few weeks 

 after the plants come above ground. These spread and 

 sometimes encircle the stems. The leaflets then brown. 

 Often the plants fall over, even before they wilt. 



Since the plants are not killed but usually recover, the 

 greatest loss lies in the destruction of the seed crop. 



Bordeaux mixture applied about three weeks after the 

 plants appear in the spring and each three weeks thereafter, 

 until August, more often if the season is wet, will control 

 the disease. All dead stalks, leaves, etc., should be 

 collected and burned in the fall. 



Wilt, acrostalagmose (Acrostalagmus alhus Preuss.). — 

 This wilt is due to stoppage of the veins by fungous 

 growth, and the chief symptom is wilting of the leaves, 

 followed by death of the stem and leaves. Sections of the 

 rootstock reveal a yellowing of the water ducts and veins, 

 which contrasts strongly with the normal white of a healthy 

 plant. This unnatural coloration of the veins may also 

 be seen upon stripping the bark from the root lengthwise. 



The disease is largely confined to the older, less vigorous 

 roots. It is advisable to remove and dry the infected 

 roots and to replace the soil of infected h>eds with new, 

 healthy soil. Soil disinfection should be employed if 

 practicable. 



Black rot {Sderotium sp.). — Black, warty growths (scle- 

 rotia) upon the rhizome indicate sclerotiose. The roots 

 are very black, but upon drying, bleach somewhat. In 

 old age this blackening may extend to the center of the root, 

 which becomes Avet, spongy, and pliable. The disease re- 

 mains in the soil some years after infection. Sick roots 



