News from the Diagnostic Centre of the Dutch Plant Protection Service
The Diagnostic Centre of the Dutch Plant Protection Service has published its Annual Report for 1992, and the following items can be noted:
1) Xanthomonas campestris pv. corylina (EPPO A2 quarantine pest) was found on hazelnut (Corylus avellana) in 1991 in the south-western part of the country and its presence was confirmed in 1992. In greenhouse experiments, several cultivars were artificially inoculated with two strains of the bacteria and were all found susceptible.
2) Erwinia chrysanthemi (EPPO A2 quarantine pest) biovar 3 was isolated on leek (Allium porrum) grown in the field. This is the first time that E. chrysanthemi is isolated in outdoor crops in the Netherlands.
3) In 1992, Bemisia tabaci (EPPO A2 quarantine pest) caused new problems in greenhouses, such as 'uneven ripening' on tomatoes, discoloration of the upper leaves of Bouvardia, and yellow leaf stalks of Gerbera. During a preliminary survey, Dutch populations of B. tabaci were compared with the A strain (cotton strain) and B strain (poinsettia strain causing symptoms of silverleaf) from USA by using electrophoresis. All tested populations belong to the B strain type.
4) In 1992, pheromone traps were placed in a garden in the province of Zeeland and attracted Cacoecimorpha pronubana (EPPO A2 quarantine pest) which was not known to be established in the Netherlands. The origin of the carnation tortrix moth remains unknown and the Dutch Plant Protection Service will further investigate the establishment of this species during the next growing seasons.
5) Severe Phytophthora root rot was observed in 1992 on raspberry. In the roots, large oospores were visible but the isolation of the pathogen was not possible. However, their morphology suggested that the causal agent was probably P. fragariae var. rubi (EPPO A2 quarantine pest).
6) Ditylenchus dipsaci (EPPO A2 quarantine pest) has been observed in the Netherlands for the first time on Helenium and Polemonium.
Annual Report 1992, Diagnostic Centre, Plant Protection Service, Wageningen, Netherlands, 113 p.