How do I identify and prevent Root Rot?
| Added by:
snoofer Last edited by:
snoofer Viewed: 500 times |
Rated by 36 users:
9.12/10 |
Contributed by:
snoofer
Submitted: 2002
Images archived:
2002
Thanks to: budmonster,
highgrade, Baudelaire
"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:
Unsterilized tools and equipment
Unfiltered water
Dead roots from previous crops
Infected plant material (i.e. clones taken from
infected moms)
Dissolved oxygen, temperature
and pythium
 The amount of dissolved oxygen
(DO) in a nutrient solution depends on the water
temperature. Cold water can 'hold' more dissolved
oxygen. A fully aerated solution at 20C/68 F is 9 -
10ppm; at 30C/86F it's 7ppm. 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 | Symptoms:
Initial:
Yellowed, droopy and wilting leaves (possibly
exhibiting mineral deficiencies). Leaf curl over - ram's
horns' - roots are unable to uptake nutrients at that
strength because they are infected.
pH becomes more acidic (pH should rise slowly in a
healthy system)
'Burnt' root tips (browning tips may also be a
result of light exposure, or over fertilization)
Reduced water consumption and rising nutrient
strength
Brown colored roots. (Note: GH "Micro" will stain
roots brown as well; stain darkens @ ppm's. Healthy root
should be white or slightly tan)
Advanced:
Brown and slimy roots with a slight to strong
rotting odor. Plant may appear healthy.
Reddish and swollen root collar, becoming blackened
over time. Eventually the plant will fall over as all
connecting tissue will have been 'eaten away'.
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."
| Management
Strategies |
top |
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.
Soil
tips:
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.
| Preventive
gardening: |
top |
Monitor plants and roots frequently. Inspect roots
for browning. Stressed plants are attacked first, so it
is important to inspect crop and remove unhealthy
plants.
Maximize aeration. Use venturis, powerheads, bubble
walls/ air curtains, air stones, and daily h2o2 usage to
increase dissolved oxygen. Allow nutrients to fall back
into the reservoir to create 'waterfall aeration'.
Use only healthy clones taken from healthy moms
(pythium is systemic and diseased moms will pass on root
rot!)
Keep ph stable, between 5.5 and 6.0
Keep air moving, circulate nutrients continuously
Keep reservoir / root zone temps low: 62-65F.(Note:
submerged pumps will increase water temperature)
Maintain a clean system. Change tank weekly to
reduce spore loads. Add only h2o2-sterilized water
Use tank additives
Other tips:
Isolate plants. Keep water culture plants isolated
in their own containers if possible.
"Run-to-waste" systems: nutrients are not
re-circulated - reduced spore loads
Use separate reservoirs/pumps to isolate systems.
Sterilize equipment shared (ie. pH meters) between
tanks
Make sure cloning mediums (especially rockwool) do
not remain saturated for too long. Drain fully after
watering.
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.
| Environmental
control: |
top |
Maximize reservoir circulation, aeration and cooling
Reverse Osmosis (RO) to remove pathogens from source
water
UV sterilizers. UV kills pathogens as nutrients are
passed through unit
Ozone. Maintain a 300-400mV level
Blow cool air through the root zone
Minimize light leaks and cover reservoir (but don't
seal) to limit algae growth. Algae will grow, reproduce
and die, adding organic material for pythium to feed on.
Algae and other slimes may coat the roots, stressing
plants even further.
*Take care using UV and
Ozone, as nutrients can precipitate out of solution.
Iron is especially susceptible.
| Chemical/Biological
additives: |
top |
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) |
| Microkill |
(kills mold/fungus/mildew/algae) |
Pro-TeKt |
(silicon) |
| Canna-zyme |
(Canna, canna.com, 15 different enzymes) |
Power Active |
|
| ATAZYM |
(Atami) |
BN-ZYM |
(bio nova) |
|
|
Zyme |
(Green Planet, 6-8ml/gal) |
| Others: Ascend/Fongarid/Consan
20)/Fosetyl-A1 (sold as
Aliette) |
For seeds,
seedlings and clones:
Use 1 drop bleach/gal when sprouting seeds using
towel method
No-damp (spray cloning domes at 5-10ml/L)
Cloning gel/powder with a fungicide
Experimental
UV Sterilizers. UV can kill waterborne organisms,
with a slow exposure to UV light. Research suggests iron
can precipitate out of solution. Pythium already
attached to surfaces in the rootzone will not flow
through the sterilizer and not be killed. Aquarium
stores sell them.
Continuous drip H2o2. According to Maximum Yield,
100ppm is required to kill pythium in solution. This
level also adversely affects small plants. Of course,
organics and beneficial bacteria in additives will also
be destroyed.
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).
Slow sand filtration. According to interet
literature, SSF can remove up to 99.7% of all bacteria.
Aquarium stores sell sand filters.
Dissolved Oxygen machines. Artifically injecting
water with oxygen may inhibit or kill pytium and other
anerobic organisms.
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| Last modified: 21:21 - Aug 29,
2002 |
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