Three microplot experiments were conducted in Chile to determine the effect of population densities of Globodera rostochiensis on the growth and yield of summer, winter, and spring sown potatoes (Solanum tuberosum). Microplots were 30-cm-diam, 50-cm-deep, concrete bottomless tubes filled with 28.3 L of soil infested with G. rostochiensis in a geometric series of nematode densities between 0 and 512 eggs/g of soil. Growth reduction of potato plants was evident only at 64 eggs/g soil on young summer potato, but occurred at 32 eggs/g soil on young spring potato. The tolerance limits of summer sown potato were 1.3 and 1.56 eggs/g soil for tuber and dry foliar weights. respectively. The tolerance limit for spring sown potato was 1.56 eggs/g soil for both parameters. The nematode reproduced poorly on summer and winter potatoes and well on spring potato, with reproduction rates of 8, 8.9, and 39, respectively. Nematode equilibrium densities for summer, winter, and spring potatoes were 39, 6
