Healthy planting material strongly contributes to prevention of, for instance, problems with Phytophthora spp., Verticillium, Xanthomonas, Colletotrichum, virus diseases, tarsonemid mites, aphids or free-living nematodes.
If growers propagate their own planting material, they must test the health status of the material in accordance with regulation (growing and propagation material has to be separated).