Soil treatment with mercurials for the control of common scab of potatoes (actinomyces scabies (thax) gussow).

The common scab (Actinomyces scabies (Thax.) Güssow) characterized by the formation of raised, level or depressed corky lesions upon the surface of the potato tuber, is a well known disease of potatoes. It is also of common knowledge today that potato scab is caused by the organism Actinomyces scabies. The scab organism may be present in the soil or may be introduced into uncontaminated soil by the use of scabby tubers. To-day, this disease occurs in practically every part of the world where the potato is grown. This widespread disease of potato is considered very serious in the United States and Canada, where it produces great losses by reducing both the quality and yield of tubers. Owing to the fact that only traces of scab precludes seed potato certification and that the production of certified seed potatoes is very important in Canada, this problem is of considerable economic importance. The problem of potato scab is one of extreme importance in the Montreal district, and has been studied for four years, with the financial assistance of the Horticulture Department of Quebec and under the direction of Professor J.G. Coulson. Experiments have been carried out at Ile Jesus and in Napierville county. Studies have been made for the purpose of testing the effectiveness of certain chemicals, chiefly mercurial compounds, when applied to the soil,in controlling common scab of potatoes in mineral and muck soils, and to determine the soil factors influencing their effectiveness