Abstract

The occurrence of soilborne diseases of potato is difficult to predict. Assessment of risk can be made from knowledge of the field into which potatoes will be sown. However, this is an imprecise way to assess risk and no set criteria are established. Soil tests are in their infancy to measure soil inoculum. In the UK, bioassays are currently considered the most effective way to measure soil inoculum. However, considerable further study is needed in order to validate them and to establish effective soil sampling regimes. Estimation of the risk of soilborne disease enables the grower to avoid disease by selecting another field, to manage disease by using husbandry or chemical control measures, or to select a resistant variety. Where risk of soilborne disease exists, monitoring disease development of certain pathogens can permit control measures to be implemented to minimise disease development on the progeny crop. Disease control is just one factor that must be considered when selecting a field. Factors such as soil type and water availability, which affect skin finish, and economic and practical factors also influence the decision.