tips & tricks
Bacillus thuringiensis is considered an all-natural pesti-
cide and some products containing it are certified for use by
organic certification institutions. Most Bt. sprays and powders
are regarded as environmentally friendly and have little or
no effect on humans, wildlife, pollinators, or most beneficial
insects. New Bt. strains are being developed all the time. Each
strain used in horticulture is given a unique number and regis-
tered with the United States Environmental Protection Agency.
Specific formulations and strains of Bt. that are approved
for use in organic production are listed on the website of the
Organic Materials Review Institute (OMRI).
Spinosad (Saccharopolyspora spinosa)
Spinosad is a biological insecticide based on chemical
compounds found in the bacterial species Saccharopolyspora
spinosa. The insecticide is a result from the fermentation of
the bacteria, a process that creates different forms of spino-
syns. Spinosyns occur in more than 20 natural forms and more
than 200 synthetic forms have been created in a lab.
The insecticide spinosad contains a mix of two
specific spinosyns, spinosyn A and spinosyn
D, in a roughly 17:3 ratio.
Unlike Bt., which must be consumed
by the pest insect, spinosad is effec-
tive by both contact and inges-
tion. Spinosad affects receptors
in the insect’s nervous system,
making the insect unable to
feed or reproduce. Spinosad
is considered an all-natural product and is approved for use in
organic horticulture by numerous nations. It is used to control
a wide variety of insects, including caterpillars, flies, beetles,
thrips, and spider mites.
Bacteria for Fungi/Pathogen Control
Another tragedy that can befall an otherwise healthy garden
is a pathogen attack. Powdery mildew, grey mold, root rot
(pythium), and botrytis can all quickly destroy a garden. Similar
to a pest insect problem, immediate action should be taken
whenever a pathogen is identified. One of the best ways to
combat these fungi-based pathogens is with the use of bacteria.
Bacillus Subtilis
“
T HE WAY the microbial
world affects our daily lives is
something most people never
think about. Even experienced
horticulturists take the beneficial
microbes that affect a garden’s
per formance for granted.”
82
grow cycle
Bacillus subtilis is a naturally occurring bacteria commonly
found in soil and in the gastrointestinal tract of humans. It
has many different uses in many different industries, but in
horticulture, Bacillus subtilis is used as a natural treatment
for powdery mildew. When sprayed directly on powdery
mildew, the strain feeds on the pathogenic fungus. When the
fungus is gone, the bacteria dies off as well since it no longer
has a food source. Unfortunately, multiple applications may
be necessary as airborne powdery mildew spores can settle
onto plants after the first batch of Bacillus subtilis dies off. It
is also difficult to apply Bacillus subtilis in the later stage of
flowering in an indoor garden because spraying any liquid
will increase the level of humidity.
Bacillus Amyloliquefaciens
Bacillus amyloliquefaciens is a species of bacterium in the
genus Bacillus. Bacillus amyloliquefaciens is a fast-growing
rhizobacteria and can quickly colonize roots. It has gained
immense popularity among hydroponic and aquaponic growers
due to its ability to destroy and keep away root rot. In horticul-
ture, Bacillus amyloliquefaciens is used to treat multiple root
pathogens, including ralstonia, fusarium, and pythium.