Maximum Yield Australia/New Zealand May/June 2019 | Page 81

“BENEFICIAL NEMATODES
ARE A GARDENER’S BEST
friend.”
Bring in Some Carnivorous Fungi
Nematophagous fungi are carnivorous and feed on
nematodes. These fungi actually set traps to snare
nasty nemotodes — either sticky traps or circular rings
that capture and kill their prey. What’s remarkable is
these fungi will only set the traps when they detect the
nematode’s ascarosides, which are the chemical cues
nematodes use to communicate with one another.
Nematophagous fungi are found in abundance where
there is rotting organic matter, such as the compost pile,
leaf mold, and decomposing bark. Adding compost, leaf
mulch, or layering your garden with wood chips will encourage the fungi that protect
your garden from parasitic nematodes.
Healthy plants resist well and perform better than plants suffering nutrient
deficiencies, even in the presence of harmful nematodes, so regularly adding
compost and organic matter to your garden serves a double function.
The most effective method of managing harmful nematodes is to use a
combination of these methods, as just one will probably not be effective on its own.
Beneficial Nematodes
Beneficial nematodes are a gardener’s best friend. Instead of attacking our plants,
they attack a wide variety of garden pests. The most helpful strains in the garden
are endoparasites of insects, which introduce Xenorhabdus sp. bacteria into the
insects they eat. This bacteria kills them within 24-48 hours and breaks down their
tissues so the nematodes can make their home inside of the insect, lay their eggs,
and feed on the decomposing tissue.
The most commonly used beneficial nematodes are Steinernematidae carpocap-
sae, S. feltiae, S. glaseri, Heterorhabditisheliothidis, and H. bacteriophora. They are
effective against many pests including weevils, cutworms, chinch bugs, white grubs,
clearwing borers, fungus gnats, and sod webworms.
These beneficials are sold
commercially as biological
insecticides. They can stay
viable for months as long
as they are kept at the
correct temperature, and
mix well with fertilisers
and pesticides. They are
considered environmentally
friendly by the EPA since
they occur naturally, are not
genetically modified, and do
not harm vertebrates. There is
no evidence insects develop
resistance to the bacteria these
nematodes produce.
How to Use Beneficial
Nematodes in Your Garden
Beneficial nematodes can be
purchased from most garden
centres, dormant in a powder.
To use, add them to water and
spray them on your plants and
soil. Be sure to remove the
screen in your sprayer so they
can get through.
Because they must be stored
at the correct temperature
to remain viable, you can
guarantee their viability
before use by adding them
to water and observing them
under a microscope.
It is important to apply
beneficial nematodes in
the correct conditions. They
require warm, moist soil to be
effective, so it is a good idea to
irrigate the garden before and
after application. Because they
travel in water, watering the
garden after application helps
to move them around and find
hosts. The ideal conditions
also include high humidity,
moderate temperatures, and
indirect sunlight. Applying
them in the morning or
evening is best.
As gardeners, we need to
understand and prevent
potential threats to our
gardens. By applying
beneficial nematodes and
using best practices to reduce
plant parasitic nematodes, we
can take care of these threats
in a way that’s effective and
won’t harm the environment.
Maximum Yield
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