Diseases of truck crops Diseases of truck crops / Ralph E. Smith diseasesoftruckc119smit Year: 1940 Diseases of Truck Crops 39 in, the head of the plant may drop off and leave a bare stump. Black rot is a very serious bacterial disease of cabbage in many parts of the United States but is rare and unimportant in California. This may be due to the fact that cabbage and cauliflower are grown here mainly during the winter or in places near the coast; the disease is favored by high temper- Fig. 20.—Cauliflower mosaic on seedling and older leaves. atures. Black rot is controlled successfully b
Diseases of truck crops Diseases of truck crops / Ralph E. Smith diseasesoftruckc119smit Year: 1940 Diseases of Truck Crops 39 in, the head of the plant may drop off and leave a bare stump. Black rot is a very serious bacterial disease of cabbage in many parts of the United States but is rare and unimportant in California. This may be due to the fact that cabbage and cauliflower are grown here mainly during the winter or in places near the coast; the disease is favored by high temper- Fig. 20.—Cauliflower mosaic on seedling and older leaves. atures. Black rot is controlled successfully by seed treatment and other precautions given under 'Control of Crucifer Diseases' (p. 44). Cabbage Black Ring.—Infected plants are sometimes dwarfed, but the principal damage from this virus disease results from necrotic spotting of the outer or older leaves which must be removed before mar- keting. When the spots first appear, they are green and vary from 6 to Ys of an inch in diameter; later a brown ring surrounds the green centers; finally the spots turn dark-brown to black, with fusing of sev- eral or more spots not uncommon. The disease is destructive on cabbage (fig. 19) grown during the winter months in the coastal and inland val- leys. Cauliflower is also affected : on this host the disease has been called 'ring mosaic' and 'necrotic ring mosaic.' The cabbage aphid is responsible for dissemination of the virus and
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