Field experiments were conducted in central Chile, in 1988-1989, to investigate the development of Globodera rostochiensis during three different potato growing seasons. Juveniles emerged from cysts throughout the year and no diapause was observed. Second-stage juveniles of the nematode in potato roots were numerous until 3-5 weeks after plant emergence and then declined. All nematode stages were present in the roots during the growing season. However, only 10-20% of the total population developed into cysts by harvest for summer and winter sown potatoes. In contrast, 40% of the population developed into cysts by harvest for spring sown potatoes. Cyst nematodes completed one generation with each potato crop; if potato was cropped repeatedly during one year, an additional generation developed on each crop. White females and brown cysts developed within 58-120 and 125-358 day degrees, respectively. Developmental time was greater in summer than in winter under conditions of central Chil
