312 



FUNGOUS DISEASES OF PLANTS 



XVIII. EARLY BLIGHT OF CELERY 

 Cercospora Apii Fr. 



Atkinson, Geo. F. Note on the Cercospora of Celery Blight. Cornell Agl. 



Exp. Sta. Built. 48: 314-316. fig. j. 1892. 

 Duggar, B. M. Early Blight of Celery. Cornell Agl. Exp. Sta. Built. 132 : 



201-206. figs. 48-50. 1S97. 

 Sturgis, W. C. On the Prevention of Leaf-Blight and Leaf-Spot of Celery. 



Conn. Agl. Exp. Sta. Rept. 21 : 167-171. 1897. 

 U. S. Dept. Agl. Rept. (1886): 1 17-120. 



Habitat relations. Cercospora Apii is the cause of the chief 

 disease of celery, beginning early in the season. It is common in 



the Atlantic states and well known in 

 the Mississippi Valley. It is also a 

 serious pest in Europe. In the early 

 stages of the disease there is a well- 

 defined spot with slightly raised bor- 

 der ; but when the spots become 

 numerous on a leaf, the latter begins 

 to turn yellow, and subsequently the 

 fungus develops abundantly its conid- 

 iophores in indefinite areas, thus giv- 

 ing the characteristic ashen or velvety 

 spots of indiscriminate form. When 

 a leaf becomes seriously injured it 

 wilts and dries. The conidia are then 

 produced in quantity over the whole 

 surface, particularly during muggy 

 days ; thus the dead leaves increase 

 many times the chances of further in- 

 fection. This disease does not usually 

 appear late in the season, being fre- 

 quently followed by the late blight 

 (Septoria Petroselini var. Apii) with which it has no genetic con- 

 nection. This fungus also occurs on cultivated and wild parsnip 

 (Pastinaca sativd) and other related plants. 



The fungus. The conidiophores and conidia of this Cercospora 

 are in no way particularly characteristic. The conidiophores and 

 spores are variable in size, depending upon the conditions under 



Fig. 145. Cercospora Apii: Ab- 

 normal Fruiting in Culture 



