THE PRESENCE AND SURVIVAL OF SOFT ROT (ERWINIA) IN FLOWER BULB PRODUCTION SYSTEMS

Abstract

Soft rot is causing increasing damage in the flower bulb industry. Bulbous ornamentals such as Hyacinthus, Dahlia, Iris, Muscari, Freesia and Zantedeschia can be infected. Soft rot in flower bulbs is mainly caused by Dickeya spp. (Dickeya spp.) and Erwinia carotovora subsp. carotovora (Pectobacterium carotovorum spp. carotovorum).To identify and detect these soft rot bacterial species in several bulbous ornamentals, standard PCR methods were used. During the last four years, research was directed to optimalize cultural practises in especially Hyacinthus to avoid or minimize bacterial soft rot. To evaluate the incidence and infection route of Erwinia spp. in the production chain of hyacinth bulbs, field plots were infected by planting diseased hyacinth, iris and Zantedeschia bulbs. Subsequently, crop rotation with different flower bulb species was applied on these field plots during two growing seasons. Harvested bulbs were analysed during the handling and storage of the bulbs for Erwinia spp. by assessing symptoms as well as by using bacterial culturing- and PCR techniques. The survival of Erwinia in water and on materials, used in flower bulb handling, was studied. Results concerning the optimalization of bulb handling during the production chain to avoid or to minimize the incidence of bulb soft rot are also presented.