Diseases of economic plants (1921) Diseases of economic plants diseasesofeconom01stev Year: 1921 GRAPE The high acreage value of the crop, the long life of the individual vine, the numerous, serious diseases to which the vine is subject, and the fact that it was one of the crops first to be commercially sprayed, renders the grape of especial interest to the plant pathologist. Black-rot I'-isg (Guignardia hidwellii (Ell.) V. & R., Phyllostida). —This wide- spread and exceedingly destructive disease, the first record of which dates back to 1861, has been responsible for the abandonment of grap
Diseases of economic plants (1921) Diseases of economic plants diseasesofeconom01stev Year: 1921 GRAPE The high acreage value of the crop, the long life of the individual vine, the numerous, serious diseases to which the vine is subject, and the fact that it was one of the crops first to be commercially sprayed, renders the grape of especial interest to the plant pathologist. Black-rot I'-isg (Guignardia hidwellii (Ell.) V. & R., Phyllostida). —This wide- spread and exceedingly destructive disease, the first record of which dates back to 1861, has been responsible for the abandonment of grape culture in many sections of the country. It is of general distribution throughout the United States, also in Europe and Asia. In 1906 in Michigan the loss from black-rot was estimated at 30 to 40 per cent of the crop; in Ohio in 1905 at 30 per cent of the crop worth $95,000. In many sections the loss is practically total unless measures are taken to check its ravages. In its most familiar form the disease con- sists of spotting and decay of the fruit. Black or brown spots, one or more in num- ber, at first infinitesimal in size, appear upon the berry. The spots enlarge with great rapidity, one spot in a few days en- compassing the whole berry and changing it into a black mass. As the rot progresses Ji d the skin remains intact, and soon the berry F:Kl{H».1 begins to shrink and shrivel until it is eventually merely a dry, hard, wrinkled, mummified fruit. The rapidity with which this change takes place is shown in the accompanying figure. Many of the berries so mummified fall to the ground, others remain upon the vine.
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