MARKET DISEASES OF FRUITS AND VEGETABLES 51 



There is no indication that the spots enlarge or that new ones develop 

 during the transit period. 



CONTROL MEASURES 



Early blight can usually be controlled by the program of spraying 

 and dusting discussed more fully under late blight of celery (p. 51). 

 (See 182, 217, 223.) 



FREEZING INJURY 



Celery that has been severely frozen can readily be recognized 

 by the flabby water-soaked condition of the leaves and leafstalks. 

 Frozen leaves if not attacked by soft rot bacteria dry out and become 

 papery; leafstalks may either become decayed or turn brown and 

 shrivel. 



There has also been recorded a second type of freezing injury 

 characterized by the appearance of isolated sunken lesions on the leaf- 

 stalks. In shape these are elliptical on the convex side and circular 

 on the concave side of the stalk. The affected tissues soon turn dark 

 brown, so that the lesions are very conspicuous. 



Inasmuch as both of the above types of injury are readily ap- 

 parent at the time of harvest it is unlikely that they will be of 

 much importance on the market. However, celery that has been 

 only mildly or partially frozen and that has recovered without any 

 markedly conspicuous effects of the injury is frequently seen on the 

 market. The only symptom by which this slight injury can be rec- 

 ognized is the loosening of the epidermis. This can readily be 

 detected by slightly twisting the affected leafstalks. Then as the 

 thin epidermal layer rises in irregular corrugations it will be seen 

 that it has separated from the underlying tissues. 



(See 175, 222.) 



GRAY MOLD ROT 



(See Carrot, Gray Mold Rot, p. 43, and Peas, Gray Mold Rot, p. 37.) 



LATE BLIGHT 



(Septorm apii-graveolentis Dorogin and Septoria apii (Briosi and Cav.) 



Chester) 



OCCURRENCE, SYMPTOMS, AND EFFECTS 



Late blight is one of the most important diseases of celery and 

 is found throughout the country wherever the crop is grown. All of 

 the above-ground parts of the plant may be affected. Unless the 

 disease is well controlled in the field, plants may be stunted or ren- 

 dered worthless for sale. Less serious losses may result from the 

 greater amount of trimming required and from the less attractive ap- 

 pearance of the marketed product. The disease is of particular 

 importance in transit and storage because the organisms causing 

 watery soft rot and bacterial soft rot readily enter through the 

 late blight lesions and cause serious market decays of affected plants. 



The disease is found only on celery and celeriac, although a fungus 

 closely related to those causing late blight is responsible for a leaf 

 spot of parsley. 



