A SEARCH FOR THE SOURCES OF ROOT KNOT NEMATODES IN COMMERCIAL ROSE NURSERIES

Between 2000 and 2002, increasing numbers of Dutch commercial hydroponic rose cultures became infested with plant parasitic nematodes, mostly by the northern root knot nematode Meloidogyne hapla. Affected growers reported production losses up to 40%. Chemical treatments against nematodes are not allowed for roses grown on hydroponics in The Netherlands. Therefore, prevention is the only way to protect crops from becoming infected. In order to decrease the number of rose crops infested with root nematodes, more knowledge about the sources and spread of these plant parasitic nematodes was necessary. A survey in and around eleven rose nurseries was conducted. Nematode sources and cultivation handlings that spread nematodes were identified. Hygiene protocols for tool disinfection and nematode free crop replacement were developed, implemented and tested at commercial nurseries. Two years after crop replacement following this protocol, formerly infected greenhouses were still nematode free. This survey has showed that it is viable to cultivate roses on recirculating hydroponic systems without plant parasitic nematodes. Conditions to be fulfilled are: a nematode-free growing-system, a 100% effective disinfection device to disinfect recirculating drainage water, nematode-free planting material and hygienic measures during the cultivation period.