Life cycle of Globodera rostochiensis and G. pallida on early potato cultivars: times are changing.

Potato cyst nematodes (PCN) are the most economically important nematode pests of potato. Early harvesting is part of a preventive management approach for very early potato varieties in Belgium. Tubers are harvested before June 20 because it is assumed that no cyst formation occurs by that date. However, this assumption might not be valid anymore because of climate changes, the availability of new cultivars (with new traits), and the increasing prevalence of G. pallida. Therefore, pot and field trials were conducted to verify the date when first cysts appear in Belgian growing conditions. The development of different populations of both species on 3 potato cultivars, viz. Eersteling (susceptible to PCN), Première (resistant to G. rostochiensis) and Ambassador (partially resistant to G. pallida) was monitored in the growth chamber with simulation of field temperatures of the season. On Eersteling and Première, males, females and cysts of G. pallida were found 8, 9 and 11 weeks (May 15), respectively, after soil infestation with cysts, when the accumulated degree-days (DD) were 261, 322 and 450. On Ambassador, females of G. pallida were never observed. Males, females and cysts of G. rostochiensis were found 10, 10 and 12 weeks (May 22) after inoculation, respectively, corresponding with 292, 292 and 398 DD. Observations in two fields and in microplots under prevailing weather conditions in 2013 revealed that cysts of both Globodera spp. were formed on June 12. Our observations show that both species of Globodera develop earlier than was assumed based on previous data.