Images archived: 2002
Thanks to: budmonster, highgrade, Baudelaire
introduction background Id & Damage Management Strategies Emergency Treatment Prevention Environmental Control Additives
"Root rot" is a common waterborne disease that can seriously affect indoor and outdoor crops year round. "Pythium" is a generic term for several different root rot and stem rot fungus species (including Pythium, Verticillium, and Phytophthora, and Fusarium). Root rot is also known as "damping-off" in seeds, seedlings and clones.
Pythium can rapidly infect crops in vegetative and flowering stages. Damage includes strain infection, reduced yields, and crop failure. Pythium is particularly damaging in high-density dwc / hydroponic / aeroponic systems, as these recirculating systems provide ideal conditions for rapid growth and spread of pythium spores. One infected plant can quickly spread rot to all plants if the system has an interconected irrigation system.
This FAQ focuses on indoor prevention and treatment options.
Pythium typically thrives in oxygen-poor (anaerobic), warm (75-85 F), and poorly circulated nutrient solutions. Heavy clay soils with poor drainage are high-risk soil planting sites.
Sources of infection:
Dissolved oxygen, temperature and pythium
Root oxygen requirement doubles for each 10C rise in root system temperature (max 30C/86F). The dilemma for the grower is that with a 10C rise in temperature, root system oxygen requirements will double, while the oxygen carrying capacity of the solution will drop by over 25%!
The nutrient DO is unable to supply the root's oxygen demands, leading to prolonged oxygen starvation. Oxygen starvation will result in slow growth, mineral deficiencies, root die-back and reduced yields. Oxygen starvation will stress the plant, leading to an eventual attack by opportunistic pathogens, such as ever-present pythium.
|Identification, Symptoms and Damage: ||top|
|Healthy roots:(budmonster)||Infected roots:anon|
Note: Root damage is permanent; new root hairs can form, but damaged roots will not regenerate. Lightly infected roots may turn white again if treated promptly.
Dead roots serve as energy sources for pythium; snip off dead roots and remove flating root piece by changing the tank frequently.
Physical test of advanced root rot:
"Brown tissue on the outer portion of the root easily pulls off, leaving a thin strand of hair-like vascular tissue exposed."
Keeping the crop healthy, vigorous and stress-free is the best "cure" against pythium. Pythium is almost impossible to 100% eradicate from an infected system; this involves starting completely over (with new mothers, containers, equipment, etc). An infected crop can be nursed along, and subsequent crops can still yield, provided the grower takes care to minimize the growth and spread of pythium in the system.
Starting with a pythium-free system is the best strategy:
Startup with a new crop:
-disinfect the system. Manual scrubbing and bleach might be necessary.
-add tap water
-disinfect the water with strong h2o2. It takes 100ppm to kill pythium outright, however this can also kill small plants. Wait 24 hours for h2o2 to dissipate to a safe level - do not add tap water to system! Add only h2o2-treated water.
-add nutrients and beneficial enzymes. The aerobic-loving enzymes will colonize the sterilized medium and system, hopefully displacing any anaerobic bacteria.
Improved soil is the first step to keeping root rot out of your garden. Adding amendments to improve drainage and aeration will decrease the chances of root rot. Use only sterilized soil/soilless mixes or heat-treated soil before use.
Removing the diseased plants and several inches of affected soil will slow or stop the spread of pythium. Avoid over watering, as saturated soil promotes anaerobic conditions. Remove and destroy roots and surrounding soil near infected plants. Use sterilized soil for transplants. Provide good drainage and avoid overcrowding plants.
Special tips for bubblers:
(highgrade) "Have an empty, sterile bucket to place the bubbling bucket into when changing nutes. The extra bucket method allows me to run a gallon of water through the pot and flush the grorocs and root mass of any salt build up. Wash the bucket prior to refilling with solution."
(Baudelaire) " maintain a humid air gap extending from the root crown down at least 4 inches. This provides the space for aerial roots to form, and keeps water away from the root collar, where root rot typically takes hold."
1. Hydrogen Peroxide root dunk
-Remove each plant from system, snip off diseased roots.
-Dip/swish each plant and container into a strong H2O2 solution, until diseased roots have been removed. Repeat as required.
2. Sterilize equipment
All equipment should be disinfected (including hoses and pots, etc) with bleach solution or 10% h2o2 solution before plants are reintroduced into the system. Rinse well.
3. Add root rot medication. Add anti-pythium additives, Vitamin B1, and fresh nutrients to a sterilized reservoir at a lower strength, at cooler temps. Reduce light levels. After a week or so, after new roots appear, add some root boost additives.
*Take care using UV and Ozone, as nutrients can precipitate out of solution. Iron is especially susceptible.
Note: H2o2 may kill enzymes used in some biological additives. Additives should be considered preventive only; not all additives may be effective.
Beneficial bacteria colonize the root system, out-reproducing root disease organisms. Some additives may "feed" on decayed roots. Additives may be added during every tank change, except for H2o2 and Ridomil.
|H2O2||(See H2O2 FAQ)||Ridomil||(1 app, systemic, toxic, 5 drops/gal).|
|FloraShield||(by GH)||Bio Bugs|
|Guardian angel||(2.5-5 ml/gal)||Bio Bran||(rambridge.com, 11 enzymes)|
|Root Shield||(americanagritech.com)||Sm-90||(citrus extracts @ 2.5 ml/gal)|
|Hydro Shield||(grotek.net)||Pro-Silica||(silicon, basic, up to 5 ml/gal)|
|Canna-zyme||(Canna, canna.com, 15 different enzymes)||Power Active|
|Zyme||(Green Planet, 6-8ml/gal)|
|Others: Ascend/Fongarid/Consan 20)/Fosetyl-A1 (sold as Aliette)|
For seeds, seedlings and clones:
H2o2 should be added to a seperate volume of water and allowed to sit for 20 minutes before adding to the reservoir. The majority of the O2 will be chemically released by the H2o2 by that point. (In high enough concentration, h2o2 will burn off the epeidermis of the roots, exposing it to attack by pathogens and damging fine root hairs).