. Fig. 4.—The crown of an alfalfa plant, showing the warts, or galls, produced by the crown-wart fungus. (Courtesy of Jones and Dresch- ler; from Cir. 326.) Downy Mildew.—In this disease of alfalfa, the upper leaves become partly yellow with the edges turned down. The lower sides of the leaves develop a delicate, fuzzy, violet-colored fungus growth, Peronospora trifoliorum. The disease is common in winter and spring but not very destructive. It disappears with dry weather. Dwarf.—Affected plants usually show a few normal stalks and nu- merous short, fine stems with small leaves coming from the
. Fig. 4.—The crown of an alfalfa plant, showing the warts, or galls, produced by the crown-wart fungus. (Courtesy of Jones and Dresch- ler; from Cir. 326.) Downy Mildew.—In this disease of alfalfa, the upper leaves become partly yellow with the edges turned down. The lower sides of the leaves develop a delicate, fuzzy, violet-colored fungus growth, Peronospora trifoliorum. The disease is common in winter and spring but not very destructive. It disappears with dry weather. Dwarf.—Affected plants usually show a few normal stalks and nu- merous short, fine stems with small leaves coming from the crown (fig. 5). The yellow color of the leaves which characterizes bacterial wilt is usually absent in this disease; in fact, the color is apt to be of a darker green than normal. Koots show yellow, discolored bands or streaks in the wood. This disease, which is apparently caused by a virus, is found mostly in southern California. Badly affected fields should be handled as ad- vised under "Bacterial Wilt" (p. 7).
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Keywords: ., bookcentury1900, bookcollectionamerica, booksubjectplantdiseases
