ask the experts
Q
A
I’m attempting to grow goldenseal in my aquaponic system, but the
roots of my plants have blackened and there was some yellow wax
oozing out of them. What can I do?
Thanks,
Van
When root systems become discolored or
darkened this generally indicates disease.
A common culprit is Phytophthera species,
the genus of a plant-damaging water mold.
Phytophthera thrive, grow, reproduce and
infect plant roots in water, saturated soil,
and along river banks and ponds. Flooded
or saturated soils are not favorable for plant
growth and can predispose plants to infection.
Anywhere significant quantities of water
collect, accumulate or flow, Phytophthora spp.
can be found. The lack of oxygen in the water is
typically what helps this fungus/mold flourish
in ponds. Usually, because of the root failure,
the plants will begin to wilt or fail completely.
It is possible that your situation could be
a different pest, however. You can bring (or
ship) specimens to a certified laboratory to get
confirmation—just check the associated costs
before proceeding with this. The downside of
mailing away from answers is that diseases
spread quickly, especially to other plants of
the same variety.
The best way to control a phytophthora
disease is before it starts. In the landscape,
water regulation and good drainage is vital.
In an aquaponic set-up, increase the amount
of oxygen in the water with something
such as an air pump or air stone. There are
meters available for checking the level of
oxygen. Make sure your pump runs at least
15 minutes each hour.
Overall, clean stock, crop rotation, sanitation,
chemicals as needed and host resistance are
among the controls that can be implemented.
Hydrogen peroxide has been successful in
controlling the disease on the roots; however,
in the case of aquaponics it may not be
successful due to dilution issues. Do some
research before trying this method.
Removing an infected plant from the water
and rinsing the roots in a light concentration
of hydrogen peroxide (three per cent),
then returning the plant to the aquaponic
system might help when done
in conjunction with the
addition of extra oxygen. As
prevention is the best way
to treat fungal diseases in
the garden, you may need
to remove the infected
plants and discard
them while you
work to improve
your water
quality, and
then re-insert
new plants.
Good luck!
Frank
Rauscher
Frank Rauscher is a certified horticulturist and
consultant for the hydroponic and landscape
industry with a background in product development.
Frank is a member of the Southern Nevada Landscape
Association and is active in the Southern California
green industry, where his focus is drought-tolerant
xeriscapes. He specializes in discovering the
“root-cause” of plant stress.
DYK?
Goldenseal is a small plant with a single hairy stem. It has two jagged five-lobed
leaves, small flowers and raspberry-like fruit. The bitter-tasting rhizome, or root, is
bright yellow or brown, twisted and wrinkled. Goldenseal can be found growing wild
in rich, shady soil in the northern United States, but it is now grown mostly on farms.
– University of Maryland Medical Center, (umm.edu)
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Maximum Yield USA | October 2016