MARKET DISEASES OF FRUITS AND VEGETABLES 3 



The pathogen often attacks seedlings and causes a serious damping - 

 off, which is characterized by browning and blackening of the young 

 plants just at the surface of the soil. Sometimes the fungus attacks 

 the roots and causes blackening and shriveling, which reduce the feed- 

 ing power of the root system so much that the plants become dwarfed. 



On the leaves light -brown spots are formed. In the older spots the 

 small, black fruiting bodies (pycnidia) are scattered or sometimes 

 arranged concentrically. When the fungus gets established it may 

 follow down the vascular bundles of the stem and enter into the .crown 

 of the root where it may cause a black, rather dry rot ; this occasionally 

 becomes serious in stored beets (pi. 1, A). Infections through the 

 side or at the tip of the main root often cause extensive decay at the 

 base of the mature beet (pi. 1,-5). This latter type of decay is some- 

 times encountered on the market in garden beets. Wounds or tissues 

 dead from other causes provide the chief points of entry into the root. 



Burning of the beet rubbish which may harbor the fungus and 

 planting only seed from healthy plants are the best methods of con- 

 trolling this disease. 



(See 21, 26, 104, 1%0.) 



Cercospora Leaf Spot 



(Cercospora oeticola Sacc.) 



Cercospora leaf spot is one of the most common and best known 

 diseases of the beet. It is of direct importance from the market point 

 of view because it disfigures the leaves, and the lesions afford points 

 of entry for soft rot bacteria. 



Small, definitely outlined spots are produced on the leaf. The 

 margin between the diseased and the healthy tissue is reddish brown 

 to purple, and the center of the spot is ashen gray to light tan. One 

 of the main effects of the disease is to reduce the effective food-making 

 area of the leaves, thus leading to the development of stunted plants 

 with poor roots. 



The causal fungus lives over from season to season mainly in old 

 beet tops. The removal of beet trash, spraying with a 4-4-50 bordeaux 

 mixture, and deep plowing are recommended as control measures. 



(See 90, 105, 106.) 



Gray Mold Rot 

 (See Globe Artichokes, Gray Mold Kot, p. 6.) 

 Internal Black Spot 



Internal black spot is a serious disease of garden and canning beets 

 grown in many localities. On the market it is found on topped and 

 stored beets, but not on young bunch beets. This trouble develops 

 in plants grown in soils deficient in boron. It may occur in various 

 types of soil, but it is most often serious in alkaline soils, which tend 

 to make boron unavailable to the plants. 



Internal black spot is characterized by black, irregular patches of 

 broken-down tissue, usually in the central part of the root. The dis- 

 colored areas are moist and of about the same texture as the normal 

 tissue. They do not dry, form cavities, or cause unusual shrinkage 

 of the root. Beets may be severely affected without showing external 



