Pythium root rot is an increasing problem for hydroponically grown vegetables. The UV disinfestation technique is commonly used in the treatment of municipal sewage sludge, biologically polluted groundwater, and residential drinking water. A similar concept was applied in the Netherlands for disinfestation of recirculating hydroponic solutions. This threshold value was influenced by pathogen concentration, hydroponic solution transmittance and other environmental factors. For effective control, the solution should be filtered to remove large particles or organic aggregates that can entrap pathogens and block transmittance of UV irradiation.
Iron chelates are major components that can greatly reduce UV transmittance.
On the other hand, UV irradiation can break down iron chelates and, as a result, reduce the availability of this nutrient to plants. Therefore, it is important to maintain a balance between the requirements for transmittance of UV light and nutrient requirements for plant growth. Thus, it may be helpful for improved plant viability to introduce beneficial organisms into the recirculating solution. An optimum level of pest management can be achieved by combining biological control with relatively low doses of UV disinfestation. An integrated approach would be environmentally and economically sound and could easily be adopted by greenhouse vegetable growers.