194 Diseases of Greenhouse Crops 



sleepy appearance, hence the name of the disease. 

 On splitting open a diseased root or stem, one finds 

 that the interior vascular bundles are brown, due 

 to the presence of the parasite (fig. 38, b.). 



The Organism. F. ly coper sici is a soil fungus 

 which may be introduced with infected manure or 

 seedlings. The fungus greatly resembles F. oxy- 

 sporum. The conidia are hyaline to yellowish, fal- 

 cate, acute (fig. 38, c and d.). 



Control, Spraying will not control this malady 

 since the parasite lives internally and cannot be 

 reached by external applications. The selection of 

 resistant varieties may offer a means of conquering 

 this trouble. Soil sterilization with steam or for- 

 maldehyde is essential. 



Black Mold 



Caused by Fumago vagans Pers. 



Black mold usually follows the attacks of the 

 white fly. The same fungus also attacks nastur- 

 tiums grown indoors. The fungus appears as a con- 

 spicuous olive-black growth on the upper part of 

 the leaves. The fungus in this case is not parasitic, 

 but usually grows on the honey dew secreted by the 

 white fly. Although the fungus is not parasitic, its 

 presence on the leaves is undesirable since it inter- 

 feres with the absorption of light by the plant. In 

 controlling white fly, the black mold fungus will also 

 be checked. 



