A study of Phytophthora spp. in declining highbush blueberry in Germany reveals that P. cinnamomi can thrive under Central European outdoor conditions

Phytophthora cinnamomi and P. cactorum were detected in soil samples from a Vaccinium corymbosum stand in southern Germany. Both species were virulent in an underbark inoculation assay and have not been reported from highbush blueberry in Germany before. While P. cactorum is a widely distributed species in nurseries and (semi)natural habitats like forests, field reports of P. cinnamomi in Germany are rare due to its sensitivity to frost. Its occurrence in an outdoor blueberry stand indicates its potential to survive Central European winter periods that tend to be increasingly mild. Phytophthora cinnamomi was also found in the substrate of young V. corymbosum nursery plants, suggesting a high degree of contamination in commercial blueberry production and demonstrating the risk of spreading exotic invasive plant pathogens via planting of infested nursery stock.