Family Liliaceas 287 



The blight in this case does not entirely disappear. 

 With the coming of wet muggy weather the epidemic 

 may begin a new course. 



The seriousness of blight is usually overlooked by 

 growers, because it usually works best when the 

 onions have attained considerable bottoms. The 

 latter are not disfigured or attacked in any way. But 

 there is an indirect loss from the disease, because the 

 food which is stored in the leaves is eventually des- 

 tined for the bulbs. When the foliage is destroyed 

 there is bound to be a reduction in yield of market- 

 able onions. 



The Organism. The conidiophores or fruiting 

 stalks come out on the surface through the leaf 

 stomata (fig. 54 a). The conidia are borne at the 

 tip end of branches of the main fruiting stalk. They 

 germinate by means of a germ tube. The oospores 

 or sexual spores (fig. 54 c, d) are formed in the same 

 way as in Pythium. The contents of the antheridium 

 is emptied into the oogonium, and fertilization takes 

 place. The oospore is thick walled, granular and oily 

 within. The mycelium of the fungus is non-septate, 

 hyaline, and derives its food by means of suckers or 

 haustoria which it sends to the host cells. 



Control. Good results have been obtained by 

 Whetzel 1 from spraying with Bordeaux. The form- 

 ula recommended is 5-5-50. The number of appli- 

 cations will vary with the climatic conditions and 

 with the severity of the disease. It is doubtful if 



1 Whetzel, H. H., New York (Cornell) Agr. Expt. Sta. Bui. 218 : 

 139-161, 1904. 



