There are various factors having an effect on the population dynamics of the beet cyst nematode Heterodera schachtii. The choice of variety is an important matter. Meanwhile three variety types are available showing susceptibility, resistance or tolerance against nematodes. Long-time studies with 46 field trials gave information on the reproduction of H. schachtii in different types and varieties of sugar beet indicating that the reproduction rate depends on the initial infestation. This has been observed in susceptible and tolerant varieties as well, whereas less reaction occurred in resistant varieties with Pf/Pi values only seldom counting >1. While growing of susceptible varieties led to an increase of nematodes population, tolerant varieties showed heterogenous results varying from a reduction to a high reproduction of nematodes. Under field conditions in Lower Saxony, Germany, tolerant varieties showed a tendency of a large reproduction potential. This results in an increase of H. schachtii populations unless measures for the reduction of infestation are applied. Data gained from field studies do not allow a clear evaluation of tolerant varieties. It is recommended to determinate the relative susceptibility of tolerant varieties in standardized laboratory investigations.
