EFFECTS OF CROP ROTATION ON SOME SOIL-BORNE PATHOGENS OF POTATO

Abstract

Crop rotations had a marked effect on the incidence and severity of wilt disease on potato crops, and consequently on crop yields. The primary cause of the disease appeared to be the "dauermycelium" form of Verticillium albo-atrum. Colletotrichum coccodes was also isolated and a few pink Fusaria were noted. The highest level of wilt occurred in the continuous potatoes and in the second potato crop of a 6-year rotation, and the lowest level occurred in a 3-year rotation. The first potato crop of a 6-year rotation had an intermediate degree of wilt. Black dot (C. coccodes) occurred at a higher level than expected and at much the same level in all rotations.