 |
In the last year indoor gardeners have reported a drastic increase
in powdery mildew, a disease more prevalent to outdoor gardeners.
Mild temperatures and wet weather, inherent to the West Coast, increase
the likelihood of powdery mildew occuring in the indoor gardening
environment.
Compiled below are the most frequently asked questions (F.A.Q.'s)
we've received about powdery mildew. The answers will help protect
your plants resulting in a productive, healthy garden.
What
is Powdery Mildew?
Powdery mildew (PM) is an indigenous,
external, parasitic, fungal disease that attacks the leaves, stems
and flowers of the host plant. PM is very common in our region and
it's airborne spores are easily transported to indoor environments.
If the right conditions exist spores will germinate and spread rapidly
through a grow room. To identify the disease look for a white, talc-like
mold growing on the leaves, stems and flowers. Growth may appear in
isolated patches on the leaves or cover the whole leaf entirely. Once
established PM may cause irregular colouring and texture (russeting)
of the leaves followed by yellowing and necrosis (death) of the entire
leaf beginning at its margins.
Will
PM Kill My Plants?
Powdery mildew alone will not result
in the death of the entire plant. The disease first affects the outer
surface of the plant followed by destruction of the outer most layer
of plant cells. This in turn inhibits the plants' ability to retain
moisture. Infected growth may die but, if properly controlled, new
growth will continue. The disease does not spread systemically. However,
the plants growth will be stunted and become vunerable to other diseases
and pests.
What
Products Can I Use to Control PM?
The most effective treatment of PM
is the use of an approved fungicide or products that have plant
protective properties. The following products have proven to be
effective:
* Sulphur - Sulphur Dust 90% WP, Safer's Defender
These natural products are safe to use and have excellent contact
fungicidal properties. Sulphur has a moderate residual effect and
is also an effective miticide.
* Benomyl -
This wettable powder has extremely low toxicity with moderate contact
and systematic (whole plant) fungicidal properties. Benomyl has
a moderate residual effect.
Potassium silicate -
This soluble form of silicon has moderate contact fungicidal properties
when used as a foliar spray (1-2 ml per litre of water). When watered
into the plant Potassium silicate
has excellent disease preventative properties and increases plant
tolerance to environmental stress.
Neem Oil - Naturoil,
Einstein
Oil
Cold pressed neem oil has moderate fungicidal properties and creates
a physical barrier to PM. It also provides excellent protection
from pests and increases growth rates.
Magnesium Sulphate - MgSO4, Epson Salts
When applied as a foliar spray (2.5 ml per litre of water) MgSO4
provides good plant protection and stress relief but only low fungicidal
properties.
|
*
|
Registered pesticide: follow label instructions regarding rates
and intervals. |
How
Can I Protect My Plants from Powdery Mildew?
The most effective way to prevent
the development and spread of PM is environmental control.
The four critical environmental factors are:
1. Humidity:
maintain a humidity level less than 65%.
2. * Air Circulation: good air circulation throughout the garden.
3. * Light Penetration: high light levels at lower plant heights.
4. Air Exchange: constant air exchange (ventilation) will remove
airborne spores from the garden preventing infection of unaffected
plants.
|
*
|
Judicious
pruning of lower branches and leaves may be necessary for proper
air circulation and light penetration. |
How
Long Will It Take to Get Rid of PM?
Be patient and diligent! Depending
on environmental conditions and the product chosen to fight the
infestation, it may take up to 3 applications to completely rid
the garden of PM. To hasten plant recovery any growth completely
covered in mould or showing signs of necrosis should be removed
and disposed of. Feeding the plant with Potassium
silicate has proven to increase the plants resistance to PM
so that new growth will be protected.
Regular use of other products that have plant protective properties
(Einstein
oil, Benomyl, Epson salts) will also help prevent a return
of the disease.
If you
require answers to any further questions please direct them
to our E-mail at info@solhydroponics.com
or call 1-800-663-0389 during regular business hours (Pacific
Time).
A personal
thank you to the customers of Solar Supply for all of the
constructive feedback.
Reference
material taken from A Gardener's Guide To Pest Prevention
and Control.
BC Ministry of Agriculture and Fisheries (1990).
|
|
