The status of biological control of plant diseases in soilless cultivation

Avoidance of plant diseases has been a major driver for the development of soilless cultivation systems. Nevertheless, diseases still occur in these systems and the need for additional control measures exist. Traditionally, control has relied on the use of chemical fungicides but environmental pressure to reduce chemical usage in the environment, and fewer active ingredients registered for use, has stimulated the development of biological methods of disease control. One approach has been to utilise microbial inoculants as straight replacements for chemical pesticides and some commercial products are now available. Sufficient root colonization and activity are key issues for effective biocontrol. Another approach has been to create growing systems with improved suppressiveness towards plant diseases. The challenge is to combine the available strategies into environmentally and economically sound soilless plant production systems with low risks for pathogen outbreaks. Soilless systems have the potential of creating a balance between a pathogen-free start and a suppressive microflora. Keywords Biological control - Disease-suppressive substrate - Hydroponics - Recirculated nutrient solution - Microbial populations - Rhizosphere - Root pathogen