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GROWERS INFORMATION -
ARTICLE - FUNGUS AMONG US |
Fungus Among Us
By: Cindy Rea
Courtesy of
Maximum
Yield Magazine
They’re everywhere! Millions of microscopic fungi spores float
through the air we breathe searching for the right environment
in which to settle down and grow.
Most of these primitive spores pose no threat to the human
population, however some are allergens that can cause those
susceptible individuals severe discomfort. Fungi play a very
important role in the biodegradation of organic matter. The
active fungi help with the decay process, which composts all
organic material back to the earth.
Mold is a type of fungus. Other types of fungi include yeasts
and mushrooms. Sometimes the term mildew is used, however they
are alternative names to describe the same type of fungus.
Mold’s most important requirement for survival and
multiplication is moisture.
There are a number of parasitic and opportunistic molds and
mildews that affect the plant world. Under ideal conditions
these insidious spores can take up residence on unsuspecting
plants, reeking total havoc. Some species of fungi are so
invasive they can wipe out an entire indoor crop in a matter
of a few days.
Almost all indoor growers will encounter one of the powdery
mildew fungi during their gardening experience. Although the
fungi that cause powdery mildew are usually different on
different plants, all of the powdery mildew diseases are
similar in appearance. In most cases, prompt recognition and
control can prevent severe damage to plants from powdery
mildew diseases.
Powdery mildews are host specific -- they cannot survive
without the proper host plant. Some varieties of powdery
mildew will germinate only on lilac while others can only live
on a rose. The fungus spores live on plant material and cannot
sustain life on any other surface. Powdery mildew has not been
shown to cause any threat to humans.
Powdery mildew occurs most commonly in areas where there is
slow or nonexistent air circulation, high humidity, and
daytime temperatures of 70-85° F. Overcrowded plants may
become easy prey for the powdery mildew fungus to germinate
and proliferate. Plants receiving high levels of nitrogen also
tend to be good hosts for powdery mildew. Light discourages
the growth of mildew, therefore, a well lit garden tends to
encounter far less powdery mildew problems. Mildew can spread
rapidly since the disease cycle can be completed in as little
as 72 hours. It commonly takes seven to 10 days from the time
of infection to the development of symptoms and secondary
spore production.
Powdery mildews, as the name implies, often appear as a
superficial white or gray powdery growth of fungus over the
surface of leaves, stems, flowers, or fruit of affected
plants. These patches may enlarge until they cover the entire
leaf on one or both sides. Young foliage and shoots may be
particularly susceptible. Leaf curling and twisting may be
noted before the fungus is noticed. Severe powdery mildew
infection will result in yellowed leaves, dried and brown
leaves, and disfigured shoots and flowers. Although it usually
is not a fatal disease to plants, powdery mildew, left
uncontrolled, will prevent normal flowering on highly
susceptible cultivars.
Prevention is always the best defense against molds and
mildews. Indoor crops should be started from seed or carefully
inspected cuttings. Molds quickly take hold and propagate.
Even a few microscopic spores will multiply rapidly and may
infest the garden. Use only sterile growing media and
equipment to ensure spores aren’t lying dormant waiting to
take up residence in a newly planted garden. It is unadvisable
to bring soil in from outdoors as it may contain fungi spores
and a host of other soil-borne bacteria and diseases.
Good air flow and ventilation are essential in minimizing
contamination as well as maintaining optimum humidity levels.
Remember, moisture is the number one criteria for mold and
mildew’s survival. High humidity levels encourage molds to
reproduce quickly and make annihilation of the intruding fungi
much more difficult. An ideal growing environment will have a
relative humidity of between 30 and 50%. A room consistently
reaching levels over 50% humidity is a breeding ground for
fungi and a host of other problems. Humidity levels can be
easily monitored with an inexpensive humidistat. Simple
oscillating fans strategically placed in the room will help
ensure good air flow. A good exhaust fan will remove stale,
moist air and replenish it with fresh, oxygen rich air.
Unfortunately, despite every precaution, there are always
opportunities for these sinister microscopic nuisances to make
their way to your grow room. They can hitch a ride on just
about anything that enters the room and eek out an existence
in a sheltered area where conditions are favourable. Before
long the mold is visible on leaf surfaces and the garden is
infested.
There are several options for powdery mildew elimination.
Sometimes removing infected leaves or plants and adjusting
humidity levels are sufficient measures to correct the
problem. Fungicides are commonly used to achieve acceptable
control. For best results with fungicides, spray programs must
begin as soon as mildews are detected. Spray both sides of the
leaves, stems and growing surface. Do not use sprays during
the flowering cycle or during lights on time.
There are other non-systemic, organic based products available
through indoor gardening shops and hydroponic retailers that
are excellent for eliminating and controlling powdery mildew.
Gray mold rot (Botrytis blight) is another common fungus found
living on both indoor and outdoor plants. The gray mold fungus
is much more destructive to plants especially during the
flowering cycle. If left unattended, gray mold can cause
damping off of seedlings and fruit rot. It can also penetrate
young buds and destroy flowers from within.
Botrytis will thrive in a humid atmosphere, however the spores
of this fungus are quite adaptable, and are able to sustain
life in a drier environment. Once moisture is delivered this
mold will germinate and spread rapidly within a couple of
hours.
Initially grey mold can appear as a grey cottony fluff on
stems and leaves. As the disease progresses it may cause stems
and flowers to appear water soaked and rotten. Grey/brown
sores may appear on stems, causing plants to fall over. The
fungus can spread quickly, wiping out an entire garden in less
than a week. Often grey mold is not detected until it has
caused severe damage. The first evidence of a problem may be
flowers falling off or crumbling when touched.
Sanitation is an essential part of gray mold control. Fallen
leaves and dead plant material should be removed from the
growing area. Grey mold thrives on plant debris. Sterilizing
pruning equipment and washing hands thoroughly after contact
with infected plant material will help eliminate the spread of
further contamination. And like powdery mildew, grey mold can
be treated with fungicides.
Most molds and mildews are easily controlled following a few
simple practices:
• Do not crowd plants.
• Adequately fertilize plants using a well balanced nutrient
formula.
• Use a preventative plant wash prior to detection of any
molds or mildews.
• Apply a fungicide at first evidence of mildew and repeat
applications as necessary. Never apply during flowering cycle.
• Prune infected plants and discard mildewed leaves and
flowers.
• Keep growing environment and equipment clean.
• Maintain humidity levels below 50%.
• Refrain from handling wet plants.
• Ensure plants are dry before lights go off.
With over 1.5 million fungal species looking for homes it is
good practice to make the overall area an unwelcoming and
inhospitable environment for any spores to settle in. Grow
rooms should start off as clean and sterile as possible. Wipe
down all of the walls, ceiling and floors with a fungicidal
wash, disinfectant soap or bleach solution. An application of
a fungus resistant paint on walls, ceiling and floor is a good
idea. Areas around windows are most susceptible to some
verities of mold, ensure they are kept clean and dry all year.
Don’t leave old draperies or upholstered furniture in the
room. Dehumidifiers can be used when humidity levels reach
worrisome levels.
Cleaning all equipment between each crop rotation will ensure
new plants are not infected with some lingering fungal spores.
Immediate attention to any disfiguration or discolouration of
plants will help identify and resolve problems quickly.
Molds and mildews that attack plants can be quite destructive
to crops. The fungi is isolated to plant material only. They
cannot live without a host plant or on plant debris. Both
powdery mildew and grey mold are not considered bothersome to
humans or pets and do not infect other surfaces of the
growroom.
Strong, well nourished plants will be most resistant to
damage, even when molds or mildews appear. Quick intervention,
at the first detection of a mold problem will further minimize
the damage.
Keeping your garden healthy and pest free is much simpler
under the right conditions. Plants will thrive and produce an
abundance of hearty fruit and flowers. |
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