MARKET DISEASES OF VEGETABLES. 31 



CELERY: BACTERIAL LEAF SPOT. 



Cause: Bacteria. 



This disease is characterized by shiny, dark-brown irregu- 

 lar, translucent or parchment-like spots on the leaves. 

 Often these lesions extend along the veins and down the 

 petioles causing a water-soaked condition. This disease 

 causes a premature yellowing and death of the leaves. The 

 lesions of this disease can be differentiated from the early 

 blight lesions by the ashen gray, opaque centers of the 

 latter and from late blight lesions by the absence of the 

 black shiny dots or pycnidia. 



Bacterial leaf spot occurs in Michigan and New York 

 celery. 



Infection takes place in the field and the disease may 

 develop, but does not spread in transit or storage. 



Severely affected stock is discriminated against because 

 of its unsightliness and because the petiole lesions destroy 

 the edible parts of the plant. 



Spraying with Bordeaux will control the disease. 



CELERY: EARLY BLIGHT. 



Cause: A fungus (Cercospora apii). 



Early blight is characterized by irregular, slate-colored 

 spots on the leaves, with ashen-gray to tan centers. These 

 can be distinguished from late blight lesions by their larger 

 size and the absence of the conspicuous black dots or 

 pycnidia. Generally early blight occurs only on the leaves, 

 while late blight occurs very commonly on the petiole as 

 well as on the leaf blade. At times early blight occurs on 

 the petioles as elongated, tan, sunken areas, and causes a 

 wilting and drying out of the leaf and petiole. This disease 

 occurs in all celery districts, but is most common in Florida 

 celery. It is favored by hot, dry weather. 



Early blight starts as a field infection, and develops in 

 transit or storage. Unlike late blight, it does not lead to a 

 rot, but causes the tissues to dry out and shrivel. 



Severely affected stock is unsightly and its market value 

 is reduced. 



Early blight can be controlled by spraying with Bordeaux 

 mixture. 



CELERY: GRAY MOLD ROT; BOTRYTIS ROT. 



(See Gray Mold Rot). 



CELERY: LATE BLIGHT. 



Cause: A fungus (Septoria petroselini) . 



Late blight is characterized by small, irregular, brown 

 spots on the leaf blade and petiole. Under transit condi- 

 tions, the lesions may be dark green and water-soaked. 

 The centers of the spots bear small, black, glistening dots, 

 the fruiting bodies or pycnidia of the fungus. This disease 



