326 Diseases of Truck Crops 



leaf either through the stomata or by piercing through 

 the cell wall of the epidermis. Early blight may be 

 controlled by spraying, see p. 337. 



Silver Scurf 



Caused by Spondylocladium atrovirens Harz. 



Silver scurf is prevalent throughout the East. 

 Fortunately the disease does not cause much direct 

 damage, since it is confined only to the exterior of the 

 epidermis. It is claimed that affected tubers are 

 subject to more rapid shrinking and drying. The 

 spots on the tubers are brown and turn silvery when 

 moistened (fig. 62 c). 



The Organism. The conidiophores are borne either 

 singly or in clusters, erect septate, with numerous 

 sterigmata which bear the spores (fig. 62 d). The 

 conidia are thick walled, elongate, many septate, apex 

 narrowed and longer at the bottom. 



Control. Seed treatment does not seem to control 

 the disease. Since silvery scurf is directly carried 

 with the seed tubers, selection of clean seed is recom- 

 mended. 



Verticillium Wilt 



Caused by Verticillium albo-atrum McA. 



Verticillium wilt is not a dangerous disease when 

 compared with Fusarium wilt. It does not kill out 



