Jan Nechwatal

Between 2010 and 2015, an extensive survey of Phytophthora diversity was performed across Portugal. Baiting and direct isolation tests obtained 48 Phytophthora taxa in 62 of 70 forest stands (89%) from 148 of 302 rhizosphere soil samples (49%) and 25 of 29 tree species (86%), and from bark cankers of Alnus lusitanica and Fagus sylvatica ; from 33 of 34 rivers and forest streams (97%); and in 12 of 13 forest nurseries (92%) from 54 of 87 root ball samples (61%) and 16 of 21 tree species (76%). The 799 Phytophthora isolates belonged to 28 known and three recently described species; one designated and two new non‐hybrid taxa; and five designated and nine new hybrid taxa. The majority, 34 Phytophthora taxa (71%), are introduced aliens in Europe while nine (19%) and five (10%) taxa are of cryptic and native origin, respectively. Phytophthora cinnamomi was the most common species in forests (56%) and forest nurseries (61%). Multiple first records for Portugal and partly Europe of both Phytophthora taxa and tree declines and new host– Phytophthora associations were found. Isolation rates from forest soil differed considerably between declining (65%) and healthy trees (10%), regardless of the tree species. The widespread infestations of nurseries with aggressive wide‐host range pathogens like P . cinnamomi , P . pseudocryptogea , P . × cambivora , P . multivora and P . plurivora , and host‐specific pathogens like P . alticola , P . quercetorum and P . quercina , will inevitably cause their further spread to the wider environment, exacerbating pathogen threats to forest ecosystems and thus weakening their resilience to climatic extremes.

Phytophthora cinnamomiandP. cactorumwere detected in soil samples from aVaccinium corymbosumstand in southern Germany. Both species were virulent in an underbark inoculation assay and have not been reported from highbush blueberry in Germany before. WhileP. cactorumis a widely distributed species in nurseries and (semi)natural habitats like forests, field reports ofP. cinnamomiin 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 cinnamomiwas also found in the substrate of youngV. corymbosumnursery 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.

In spring 2019, Capsicum annuum plants, var. Jalapeno M, from an organic greenhouse production site in Bavaria, Southern Germany, showing typical symptoms of a bacterial leaf spot disease were sent...

Validation data is presented for a conventional PCR test that specifically detects the quarantine pathogen Pantoea stewartii subsp. stewartii in maize leaf and seed samples and does not cross‐react with the non‐pathogenic P. stewartii subsp. indologenes. The PCR tests currently recommended by the EPPO Diagnostic Protocol PM 7/60 (2) for initial screening bear the risk of false positives as they detect both subspecies of P. stewartii. The test presented here has high analytical sensitivity (10² cells mL^–1 in leaf extracts, at least 10³ cells mL⁻¹ in seed extracts), high repeatability and high reproducibility and performed well on the two matrices tested: maize seed and leaf extract. Its improved analytical specificity and analytical sensitivity compared to the currently recommended tests lead the authors to suggest that this test should be included as a first screening test in the diagnostic protocol for P. stewartii subsp. stewartii when it is next revised.

Summary: An analysis of incidence of Phytophthora spp. in 732 European nurseries producing forest transplants, larger specimen trees, landscape plants and ornamentals, plus 2525 areas in which trees and shrubs were planted, is presented based on work conducted by 38 research groups in 23 European countries between 1972 and 2013. Forty‐nine Phytophthora taxa were recorded in 670 nurseries (91.5%); within these nurseries, 1614 of 1992 nursery stands (81.0%) were infested, although most affected plants appeared healthy. In forest and landscape plantings, 56 Phytophthora taxa were recovered from 1667 of 2525 tested sites (66.0%). Affected plants frequently showed symptoms such as crown thinning, chlorosis and dieback caused by extensive fine root losses and/or collar rot. Many well‐known highly damaging host–Phytophthora combinations were frequently detected but 297 and 407 new Phytophthora–host associations were also observed in nurseries and plantings, respectively. On average, 1.3 Phytophthora species/taxa per infested nursery stand and planting site were isolated. At least 47 of the 68 Phytophthora species/taxa detected in nurseries and plantings were exotic species several of which are considered well established in both nurseries and plantings in Europe. Seven known Phytophthora species/taxa were found for the first time in Europe, while 10 taxa had not been previously recorded from nurseries or plantings; in addition, 5 taxa were first detections on woody plant species. Seven Phytophthora taxa were previously unknown to science. The reasons for these failures of plant biosecurity in Europe, implications for forest and semi‐natural ecosystems and possible ways to improve biosecurity are discussed.