Tips on managing disease in your hydroponic system

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Understanding the 3 options to manage root born disease issues.

Fortunately and unfortunately there are so many ways to manage pathogens in a hydroponic nutrient solution. Having options is great but these options can be difficult to navigate for new growers. Hopefully this overview comparing three popular management styles makes it easier to understand the tradeoffs between each.

Pictured above: Rhizoctonia and other root rot pathogens can spread through a recirculating hydroponic nutrient solution infecting all susceptible crops. Sterilization methods can help reduce the spread of spores in the nutrient solution while microbial inoculants can help reduce the chance of infection in individual plants.

Nutrient Solution Disease Management

Popular Methods: UV, Ozone, Hydrogen Peroxide, ChlorineMethod: InoculantsMethod: Inoculate seedlings and use sterilization techniques in grow out system
Depending on method, the sterilization process can be quantified/measured (ORP, ppm…)Difficult and expensive to quantify/measureDifficult to measure effects of inoculant but sterilization techniques may be quantifiable
If fails, environment is very susceptible and very difficult to recoverFailure may appear as partial crop loss but it is difficult for pathogen to completely takeover systemInoculants provide protection to root system if sterilization fails. If inoculants fail, the sterilization efforts makes it less likely pathogens reach root system.
Requires tight control, too little and pathogens live, too much and there is risk of damaging plants.Difficult to control beyond add and hope.Requires less tight control than pure sterilization. Goal is to reach high enough levels to sterilize nutrient solution in reservoir and irrigation lines but it is ok if target for sterilization (ORP, ppm…) is not achieved at root zone.
Difficult to ensure sterilization efforts reach entire system (reservoir, root zones, irrigation…)Microbial population naturally grows and spreads throughout entire systemLess concerned if sterilization methods do not evenly reach all parts of the system. Root zone has its own protection.
Depending on method, there may be effect on micronutrients in solutionGenerally improves nutrient availability/uptakeDepending on sterilization method there may still be an effect on micronutrients in solution. Depending on inoculants, there may be improved uptake of nutrients but it will still be necessary to account for loss of micronutrients due to sterilization method.
Depending on method, there may be some biofilm controlUnlikely to get 100% biofilm management but if correctly inoculated the biofilm should stabilize and not get out of control.Similar biofilm control as sterilization method alone.
hydroponic arugula grown with microbial inoculants
These arugula plants were all grown in hydroponic floating raft systems using only microbial inoculants for disease management in the nutrient solution. The plant on the far right is displaying symptoms of a root rot even though it was provided the same inoculant as the other two plants. From left to right the plants were grown in nutrients solutions with 30 ppm, 7.5 ppm and 2 ppm dissolved oxygen. A microbial inoculant may not provide much disease control if the nutrient solution conditions are not favorable for the beneficial microbes and the plant is weak from stressful root zone conditions.

There are many more decisions to make after selecting a general management style. For biological or hybrid technique, what inoculant and where should it be applied? For sterilization or hybrid, what is the best sterilization method for the specific farm design and what constraints can inform that decision? 

For more information on the many options for managing pathogens in a recirculating nutrient solution I recommend reading “Disinfestation of recirculating nutrient solutions in greenhouse horticulture” by David Ehret, Beatrix Alsanius, Walter Wohanka, James Menzies and Raj Utkhede. For more information on the many other considerations when designing a hydroponic farm for leafy greens production I recommend reading “Roadmap to Growing Leafy Greens and Herbs” by Tyler Baras (that’s me!).

To continue the conversation, email us and schedule some time with either Chris Higgins or our newest grower consultant Tyler Baras (aka The Farmer Tyler.)

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