Effect of Clover, Ryegrass and Winter Wheat Used in Rotation with Potatoes on the Incidence of Disease and Soilborne Pathogens in Potatoes

Abstract

The incidence of soilborne potato pathogens was monitored in fields planted in 1986 to clover, ryegrass, or winter wheat, and followed with potatoes in 1987. The incidence of Colletotrichum coccodes, Fusarium solani, F. sambucinum, F. oxysporum, and Verticillium albo-atrum in rotation crops did not affect recovery of these pathogens from root and stem tissue of the potato crop in 1987. Low levels of V. dahliae were isolated from both winter wheat and ryegrass root and crown tissue in 1986. The incidence of V. dahliae and wilted plants was significantly higher in potatoes following winter wheat and ryegrass than following clover. The incidence of Rhizoctonia solani increased throughout the 1986 growing season in clover and ryegrass whereas levels found in the winter wheat crop were constant and lower. At the end of the 1987 growing season, potato fields following winter wheat had a higher incidence of R. solani in the tissue below the soil line than in potatoes planted after ryegrass or clover. The incidence of R. solani in the potato crop was also positively correlated (P=0.05) with the occurrence of severe stem rot. Stem rot in potatoes and tuber yields were not significantly affected by the three previous crops.