A differential equation is used to simulate the population dynamics of
the sugar beet cyst nematode Heterodera schachtii in rotations compri
sing host and non-host crops. Transition probabilities between develop
mental stages are formulated as density dependent. The number of gener
ations within one year is determined by the prevailing environmental c
onditions. The parameter set is calibrated to standard cropping system
s. Although the structure of the model is kept simple, the model outpu
t compares well with different sets of experimental field data. The mo
del can be used to forecast realistic long-term changes of nematode de
nsity in sugar beet rotations.