How do I recognize and prevent root rot in
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Root Rot/Stem Rot is a
common disease that affects hydroponics, soil and
soilless systems. Growers running soil and soilless
systems should be aware of the environment that pythium
thrives in, and actively improve their room/planting
site conditions. Soil growers do not have the luxury of
looking at their roots, so they should anticipate
problems and recognize the early symptoms of pythium
Root/Stem rot is almost impossible to
treat because it is systemic (internal) in nature. Even
in an advanced stage root rot may go unnoticed, with
above ground growth appearing normal. Growth and yield
however, can be drastically reduced. Think of pythium as
flesh eating disease for plants! Some
external symptoms to look for:
Slow growth for no apparent reason
(Narky) Often the top of growth
shoots will also become limp and buckle over
Leaves turn yellow starting at the bottom-most node,
from the leaf tips inwards
Reddening root collar, turning to a brown/black ring
girdling the entire stem.
Eventually this black
ring will turn necrotic and the external tissues will
appear "eaten" away. The internal vascular tissues will
still function, and allow the transpiration of water and
nutrients (The plant will appear healthy). Within a
week, the dissolved stem will no longer support the
weight of the plant, and it will fall over!
Common causes of pythium in soil:
Root rot is also known as damping-off disease
because it commonly occurs when plants are in the
seedling stage, due to:
Drainage - MJ requires well drained soil, so add at
least 25% Perlite to all soil mixtures. Substitute
sterilized pebbles or rocks (be sure to bake this in
your oven for 10-15 minutes to sterilize).
put an inert medium (ie. gravel/peagravel/popocks) at
the bottom of the container (with your soil/sloilless
mixture on top) to avoid saturation of the lowest layers
of the soil and provide full draining.
Overwatering Growers should allow their plants
to (almost) dry out before re-watering (Do the Lift
test). This wet-dry watering cycle helps to minimize
over watering, stagnant water conditions and low
dissolved oxygen within the medium.
Stagnant Water Soil moisture that is not
absorbed rapidly turns stagnant; the plant quickly uses
up any oxygen within the water, then is unable to
respire further, resulting in moisture low in o2.
Pythium thrives in low-oxygen (anaerobic) conditions.
Plants should be watered at the start of their
daily light cycle, so they are able to transpire much
(if not most) of that supplied water, resulting in a low
soil moisture content and higher oxygen content during
the low-growth night cycle. A highly porous soil medium
combined with a low soil moisture % provides a higher
gas exchange. This is important during night cycle root
4) Low light
/ Low temps Plants in low light conditions does
not get adequate energy for healthy growth. Low light
will cause plants to stretch, grow slowly, yield poorly
and causes general stress. Lowlight also usually results
in lower temperatures, resulting in slow growth and
Under low light/cool temp conditions,
soil tends to remain cool and saturated for extended
periods. Under these circumstances, the plant is unable
to actively transpire moisture out of the soil.
Oversaturated soils do not allow adequate gaseous
exchange, and oxygen becomes depleted.
plants are more susceptible to disease.
Solution: expose your outdoor plants to more
light, allow the soil to warm up by removing excess
surface mulch. Plant after June 1 to avoid lower soil
temps. Plant on raised burms to increase soil temps and
can add 5ml/L of No-Damp (a fungicide) to their potting
mediums when mixing up. No-Damp discourages root growth
(Narky) Stem rot is caused by
overwatering and occasionally by mulching to close to
the stem while a plant is young. Remove any effected
areas of your plant immediately! (Be merciless)
Correcting your watering practices and spraying with a
fungicide can bring a plant back to health.
| Last modified: 15:19 - Feb 20,