News from the Diagnostic Centre of the Dutch NPPO
The EPPO Secretariat has extracted the following points from the 1999 and 2000 Annual Reports of the Diagnostic Centre of the Dutch NPPO.
Surveys for Bursaphelenchus xylophilus (EPPO A1 quarantine pest) were carried out as part of an EU-wide programme. They were mainly done in locations showing poorly growing- or recently dead pine trees, and near places where frequently imported packing material from areas where the nematode occurs is stored. In 2000, 60 sites were surveyed and 108 wood samples were tested. B. xylophilus was not found.
Surveys for Diabrotica virgifera (Coleoptera: Chrysomelidae - EPPO A2 quarantine pest) continued in 2000. Pheromone traps were installed in maize fields which were considered at risk (in the vicinity of military airbase receiving material from the former Yugoslavia, near major harbours, in intensive maize-growing areas). No D. virgifera were caught in 2000.
In 1999, Ditylenchus dipsaci (EPPO A2 quarantine pest) was observed for the first time on bulbs of Eremurus.
Studies on the taxonomy and diagnosis of Guignardia citricarpa (EPPO A1 quarantine pest) were carried out. Phytosanitary regulations are restricted to citrus-pathogenic strains of G. citricarpa, but pathogenic strains cannot be distinguished morphologically from non-pathogenic strains. Genetic studies revealed, among G. citricarpa strains, two distinct and homogeneous clades. Clade 1 contained strains isolated from citrus fruits showing classical black spot lesions (1-10 mm) often containing pycnidia. Clade 2 contained endophytic strains from outside the citrus family, as well as strains from asymptomatic citrus fruits or fruits showing minute spots without pycnidia. On specific growing media, clade 1 strains were slow-growing compared to clade 2 strains. Clade 1 strains produced yellow pigment on oatmeal agar, whereas clade 2 strains did not produce any. Some morphological differences could be observed on conidia between clade 1 and 2 strains, but not on pycnidia. The fast-growing non-pathogenic strains of G. citricarpa will be proposed as a new species. PCR primers have been developed and can distinguish between the two Guignardia species.
Impatiens necrotic spot tospovirus (EPPO A2 quarantine pest) was found in 1999, 34 times, in 20 different plant species from the Netherlands and from other countries. It was found for the first time on Fatshedera japonica, Freesia, Helianthus annuus, Hoya carnosa, Kalanchoe nitriformis, K. thyrsiflora, Peperomia rotundifolia, Trachelium. In 2000, it was found 31 times, in 21 different plant species from the Netherlands and from other countries. It was found for the first time on Ageratum houstonianum, Echeveria, Streptocarpus, Zantedeschia odorata.
In 1989, Meloidogyne chitwoodi (EPPO A2 quarantine pest) was found on Potentilla and Dicentra spectabilis.
In 2000, 22,000 samples were tested by the Dutch NPPO and 38,000 by NAK for the presence of Clavibacter michiganensis subsp. sepedonicus and Ralstonia solanacearum (both EPPO A2 quarantine pests). The 2000 situation for C. michiganensis subsp. sepedonicus has already been presented in EPPO RS 2000/165. For R. solanacearum, in 2000: 29 places of production were found infected (in 1999, 43 had been found infected). The number of findings is decreasing (now less than 0.05% of the total number of tested samples were found positive). As in previous years, some of these infections could be explained by clonal relationships between potato lots, whereas others could be explained by use of contaminated surface water or machinery. In 2000, 8,198 duplicate samples and 133 samples of Solanum dulcamara were tested. Water samples were taken from areas already known to be infected. Bacteria were detected in 10.5% of water samples and in 9.3% of weed samples. As a result, 32 areas were defined as ‘risk areas’ in which the use of surface water has been prohibited. Work is also continuing on the development of diagnostic methods for both potato bacteria.
In 2000, Ralstonia solanacearum race 1 biovar 3 (EPPO A2 quarantine pest) was detected for the first time on Curcuma alismatifolia imported from South Africa
Stephanitis takeyai (Heteroptera: Tingidae – EPPO Alert List) was reported from a single Pieris japonica plant in a private garden in Boskoop, Province of Zuid-Holland in 1994. The population was eradicated with the destruction of the infested plant. However in 1999, two samples with high numbers of nymphs and adults of S. takeyai were collected from Pieris japonica in another private garden in Boskoop. A limited survey in private gardens in this area showed that the vast majority of P. japonica plants were infested, but the insect was not found on other plant species. Some P. japonica plants were heavily damaged due to the sap-feeding activities of large populations. This suggest that the pest has already been present for a number of years in the area of Boskoop.
Tomato spotted wilt tospovirus (EPPO A2 quarantine pest) was found in 1999, 38 times in 14 different plant species from the Netherlands and from other countries. It was detected for the first time in Micronetta. In 2000, it was found 25 times in 13 different plant species from the Netherlands and from other countries. It was detected for the first time in Ajania pacificum and Clematis.
In 2000, Xanthomonas axonopodis pv. dieffenbachiae (EPPO A1 quarantine pest) was detected for the first time in 2 plants of Aglaonema imported from Puerto Rico.
Annual Report 1999, Diagnostic Centre, Plant Protection Service, 119 pp.
Annual Report 2000, Diagnostic Centre, Plant Protection Service, 132 pp.