Population decline of potato cyst nematodes (Globodera rostochiensis, G-pallida) in field soils in Northern Ireland

The decline rates of potato cyst nematodes (Globodera rostochiensis, G. pallida) in agricultural soils in Northern Ireland were monitored over 13 years. Initial decline rates appeared erratic due to variable cyst ages and high Standard Errors at low population levels, but were, generally, slower than those previously reported with less than 10% annual decline within each category of assessment (cysts sample(-1), eggs g(-1) and eggs cyst(-1)). Rate of decline was not affected by the range of soil types studied, but regular cultivation of infested land appeared to accelerate it. Juveniles present within cysts over 30 years old were either dead or inactive and such field populations were considered non-viable.