ematodes can either be a
gardener’s best friend or worst
N enemy.
Plant parasitic nematodes
invade our gardens and cause
yellowing leaves, stunted growth,
and poor harvests. Beneficial
nematodes are powerful allies that
feed on harmful bacteria, fungi,
insects, and other nematodes that
want our crops for themselves.
Beneficial nematodes also break
down organic matter and recycle
nutrients in the soil.
Nematodes are microscopic round
worms that can range in size from
one-fiftieth of an inch up to several
inches long. They were some of the
first organisms to exist on the planet,
having been around for an estimated one billion years. They live in water
and soil and, depending on the type, feed on bacteria, fungi, protozoans, other
nematodes, insects, plants, animals, and even humans. They are a vital part
of the soil food web, serving as predators, prey, and nutrient recyclers.
There are more than 15,000 known species of nematodes on the planet,
with an estimated 15 per cent of the species being parasitic towards plants.
They are so abundant that if you were to remove everything on earth except
nematodes, we would still be able to see an outline of everything on Earth.
In fact, just one handful of soil can contain millions of them.
Harmful Nematodes
Plant parasitic nematodes are only about one-fiftieth of an inch long, with
smooth, unsegmented bodies. Most are long and slender, while some species
are more pear shaped. They have sharp, pointed mouths, called stylets, which
puncture cell walls and allow them to feed on tissues.
“Nematodes ARE A VITAL PART OF
THE SOIL FOOD WEB, SERVING AS PREDATORS,
PREY, AND NUTRIENT RECYCLERS.”
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Maximum Yield
There are four classifications of
plant parasitic nematodes. Migratory
ectoparasites feed on the outsides of the
roots. Sedentary ectoparasites burrow
their heads into the roots to feed and
stay there. Migratory endoparasites
tunnel into the roots and then search
for another host when they are done
feeding. Sedentary endoparasites
burrow into the roots and stay there
permanently to feed. Nematodes will
also eat parts of the plants above ground
at different times in their life cycle.
They can cause some serious harm, to
the tune of an estimated $77 billion in
damages to crops worldwide. The most
common plant parasitic nematodes
are root knot nematodes. They get their
names from the damage they cause to
root systems. When they puncture the
root and move in, they actually expand
the size of the root to make more room
for themselves and their offspring.
When you dig your sick plants up at the
end of the season, you’ll find the roots
have knots in them.
Symptoms may include yellow wilted
leaves, signs of infection, stunted
growth, and poor yield. Nematodes
also present as patches of poor growth
in an otherwise healthy field, which
may spread if left untreated. If you
suspect nematodes are the cause of
the problem, you can gently lift the
plant out of the ground and examine
the roots. You may see root rot, injured
root tips, small lesions and knots, or
excessive root branching.
The symptoms may be mistaken for
other issues until you dig up the plant,
and sometimes there is no damage
to the plant at all. Healthy plants can
actually tolerate small infestations
without suffering a loss in production.