Disinfestation of recirculating nutrient solutions in greenhouse horticulture

Recirculating nutrient systems offer a good method to control nutrient leac hing from greenhouses into the environment. However, the potential for the rapid spread of root diseases is the main hindrance to adoption of recircul ating nutrient systems by the greenhouse industry. This review discusses an d compares five broadly different methods of disease control in these syste ms, namely heat, filtration, chemical, radiation and biological control. Ea ch has strengths and weaknesses, but all have been found to be effective in terms of pathogen control. Sterilization (heat, oxidizing chemicals, UV ra diation) and membrane filtration methods are generally very effective, but may adversely affect beneficial microorganisms in the recirculated solution . Slow filtration and microbial inoculation methods are less disruptive of the microflora, but effectiveness may vary with the pathogen. Microbial ino culation holds the promise of very targeted disease suppression, but few pr oducts are commercially available.