Hydroponic Root Rot

Hydroponic Root Root

Preventing & Managing Hydroponic Root Pathogens

Hydroponic root rot is an avoidable and treatable crop disease. Note that browning and decaying roots are more of a symptom and not a particular plant disease, identifiable as brown mushy roots. Hydroponic root rot results when a disease causing organism (pythium, fusarium, etc) is introduced or is present and conditions prevail that favor the growth and development of the organism in the crop’s root zone. In crop management terms, this is referred to as the Crop Disease Triangle, ie three factors create the situation:


  1. Host (plant, roots)
  2. Pathogen/Vector (disease causing organism)
  3. Favorable Conditions (warm temperatures, anaerobic)

From the above, all three sides need to occur for the disease triangle to occur, leading us to the best root rot control measure, which is prevention.

Above: these roots are displaying severe symptoms of hydroponic root rot


Above: Healthy root system


Preventing Hydroponic Root Rot


Following Current Culture H2O’s protocol for high pressure aeroponics, deep water culture and recirculating deep water culture systems will all but eliminate the chance of crops exhibiting hydroponic root rot. Proven production practices combined with well designed, refined and built hydroponic systems provide repeatable results.  Additionally, the fundamentals and practices are entirely scalable, whether Residential, Professional or Commercially cultivating water culture crops.

Above: This water supply is likely to encourage pathogens for hydroponic crops.


However, this is information all types of water culture growers may benefit from, so let’s have a brief discussion on some of the areas that need to be managed and why to prevent hydroponic root rot from occurring.


1. Eliminate organic matter – Whether introduced in a transplant medium, water source or by using nutrient additives not appropriate for the system type, it is imperative to maintain a “zero tolerance” for organic matter in the system. Additions of organic matter, however small, should be regarded as contaminants in well run hydroponic systems.  Examples of ingredients may include carbohydrates, enzymes, vitamins, beneficial microbes, etc. This is typically a grower’s number one source for introducing the Pathogen/Vector side of the Crop Disease Triangle.


TIP: ORP Management helps reduce or eliminate scale and microbial activity in the root zone


2. Clean, filtered water only – As mentioned above, raw source water may contain plant disease causing microorganisms or other vectors/substances that can contribute to symptoms of hydroponic root rot. Reverse Osmosis water is preferred for both crop performance and maintaining a healthy, clean nutrient solution. Consult CCH2O SOPs for recommend water handling and storage outside of the hydroponic system.


3. High purity hydroponic grade fertilizers only – Besides ensuring that no organic matter is present in your nutrients, the chemical composition and balance of nutrient ions present in hydroponic solutions counts big. Some sources, like urea or ammonium can cause swings in pH and nutrient availability, creating stresses on crops that leave them more vulnerable to hydroponic root rot. Cultured Solutions nutrients and additives are an excellent example of modern formulations intended for hydroponic use.


4. Maintain optimal root temperatures – In a warm grow room, some growers may find it challenging to maintain 68 to 70 deg F temperatures in the root zone.  As the solution gets warmer or cooler than optimal, conditions begin to favor pathogens more than root health.  Growers may find this important pillar to crop health a challenge, however, with a high quality Hydroponic Chiller, maintaining optimal root temperatures in hydroponics is made easy and consistent.


5. Maintain consistent aeration and dissolved oxygen levels in the hydroponic nutrient solution.  Hydroponic root rot thrives in low oxygen and stagnant conditions.  Keeping the nutrient solution well aerated and circulated maintains conditions favorable to healthy roots and strong nutrient uptake by crops.

6. Root zone IPM – mycostop, HOCl (UC Roots / Clear Line)


Identifying Hydroponic Root Rot


Healthy hydroponic roots typically range from white to light tan and appear firm–think pasta noodles done “al dente”.  Some crop types and nutrient solutions will maintain healthy roots that may not appear 100% white.  However, if following CCH2O protocol you can expect firm, white fuzzy roots that show little or no signs of discoloration; the calling card of maximum water and nutrient absorption potential.


Above: a hydroponic root system at the onset of root disease.


If roots appear brown, are covered in bio film or are soft and mushy, it is likely that they have an advanced onset of hydroponic root rot. Above the root zone, yellowing leaves, weak limbs and slow crop development are an indicator that trouble may be lurking down below in the root zone.

If Pathogens Pressures are Present:


  • Reduce lighting to 75% during pathogen pressures
  • Drain system volume, refill with nutrient at 50% strength
  • Maintain recommended dosage of Hypochlorous Acid with target ORP @ 300-350mV
  • Inoculate solution with Mycostop Biofungicide, following CCH2O defined SOP
  • Drain system weekly @ 50-75% and refresh with 50% strength solution

*this will help expel excessive exudate and microbial mass


Once plant health improves:


  • Increase lighting back to 90-100%
  • Increase nute strength to 85-90% recommended strength
  • Maintain recommended dosage of Hypochlorous Acid with target ORP @ 300-350mV
  • Continue using Mycostop on Bi’Weekly basis as outlined in CCH2O SOP
  • Reduce frequency of drain out, allowing solution health to stabilize