Results of a survey on plant protection in organic nursery production in Germany

In Germany a survey relating to plant protection in 31 organic production nurseries was conducted in 2003. At that time 44 nurseries were run organically. The survey was carried out by interviewing the nurserymen on their premises. The organic production nurseries were very heterogeneous in size and structure. Nearly all growers inspected their crops regularly for plant diseases, pests, and weeds. If plant protection problems arose, nurserymen consulted primarily technical literature or asked other colleagues. The occurrence of economically significant causes of damage varied very much from nursery to nursery. A great range of different disease species were recorded by the growers without indicating a particular one. In contrast sucking insects like aphids and scale insects, vertebrates, spider mites and black vine weevils were mentioned as pests playing a major role. Common couch and creeping thistle were reported as weeds difficult to control. The most important criteria for controlling weeds, pests and diseases were economic thresholds, tolerance by the customer and operating procedures. A systematic change of plant selection was an important instrument in organic nursery production to avoid or minimise infestations with viruses and pests. In existing stock, nurserymen controlled harmful organisms and undesired weeds by various preventive and direct measures. Growers take a lot of different measures to encourage the occurrence of beneficials. They set up additional food sources and refuges with hedges, green fallow, tolerating weeds and wood or stone piles.