356 Diseases of Truck Crops 



leaves of the stalk, producing irregular spots without 

 a definite boundary line. When the spots become 

 numerous the foliage withers and dries up (fig. 69 a, 

 b, c, d). The disease attacks the leaves as well as 

 the stalks, rendering the affected plants useless so far 

 as market is concerned. In storage, plants affected 

 with late blight will keep very poorly or rot alto- 

 gether. 



TTie Organism. The fungus mycelium is hyalin, 

 septate. The pycnidia (fig. 69 e) are olivaceous, 

 prominent, and abundant in the spots. The pycnidia 

 are filifom, straight or cmved, hyalin, and many 

 septate. 



Control. According to Rogers,^ late blight may 

 be controlled by spraying with 5-6-50 Bordeaux. 



The first two applications should be given the 

 seedlings in the seed bed. In the field the first 

 sprajnng should be given about six weeks after trans- 

 planting and continued once a month until the rainy 

 season is over. With the advent of heavy rains, 

 spraying should be done once every two weeks. 

 Besides spraying, shading also seems to keep the 

 disease in check. In sprajang celery great care 

 should be exercised to use a sprayer which is operated 

 by a pressure of not less than 1 50 pounds. Where this 

 is overlooked, large drops of the Bordeaux mixture 

 maybe deposited on the leaves and stalks, which upon 

 drying may deposit copper salt sufficient to harm 

 the consumer. Sprayed celery should be carefully 

 washed and dried before shipping. 



' Rogers, S. S., California Agr. Expt. Stat. Bui. 208 : 83-1 15, 1911. 



