. Canadian journal of agricultural science. Agricultural Institute of Canada; Agriculture. 234 SCIENTIFIC AGRICULTURE March. 1922. Diseases of the Potato By B. T. Diekson. Professor of Botaiiv. MacHldiiald College. {Co)i{inued.) Group 5. Disease Caused by an Ascomycete. Wilt and Stem-Rot or Stalk Disease. Sclerotial diseases of the jx-tato have been reported from many countries within recent years. That known as "stalk dis- ease" caused by Sclerotinia sclerotiorum is common in the West of Ireland and in the northern damper parts of England and Scotland. Growers believe that it is the
. Canadian journal of agricultural science. Agricultural Institute of Canada; Agriculture. 234 SCIENTIFIC AGRICULTURE March. 1922. Diseases of the Potato By B. T. Diekson. Professor of Botaiiv. MacHldiiald College. {Co)i{inued.) Group 5. Disease Caused by an Ascomycete. Wilt and Stem-Rot or Stalk Disease. Sclerotial diseases of the jx-tato have been reported from many countries within recent years. That known as "stalk dis- ease" caused by Sclerotinia sclerotiorum is common in the West of Ireland and in the northern damper parts of England and Scotland. Growers believe that it is the most serious potato disease in these dis- tricts next to Late Blight. A similar di- sease caused by the same fungus attacks tomato, artichoke, sunflower, bean, squash, cucumber, carrot and turnips (Cotton, ) in Great Britain. Bisby has report- ed a sclerotial disease of sunflower from Manitoba which is common also in Quebec and elsewhere. MacAlpine found a scle- rotial disease of potato in Australia, which he attributed to S. sclerotiorum, Carpen- ter one in Hawaii caused by S. Rolfsii, and Pole Evans reports one from South Africa. During the summer of 1921 Mr. 0. W. La- chaine found 10 per cent infection of a 4 acre field of potatoes in Restigouche Coun- t}', New Brunswick, and four other fields of 3 or 4 acres had from 1 per cent to 2 per cent infection. The photograph (Fig. 11) is from Lachaine's material. Happily the disease according to present indications does not appear to be serious on potatoes in this country although more work must be done on it to determine this authorit- atively. Symptoms. The first signs of the disease are patches of whitish mycelium on the outside of the potato s'em at, or just above, ground level. If the weather is humid profuse mycelial growth occurs with the later development of external sclerotia. At first these are whitish, turning black and finally falling to the ground. At the same time the my- celium gradually penetrates the inner tis
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