Agriculture Reference
In-Depth Information
at maturity,
females lay eggs
on root surface
juveniles invade root tips
eggs
galls form on roots
female nematode
gall
eggs hatch
juveniles in soil
juvenile develops in egg
Fig 2.29 Life cycle of root-knot nematode.
from 1-10 mm in diameter, develop all over the roots. In
severe infestations, heavily galled roots may rot away,
leaving a poor root system with a few large galls.
growth are also ideal for the development of root-knot
nematode.
Management
Specific management measures depend on the particular
crop. These are some general management systems for root-
knot nematodes in perennial crops:
Biology of root-knot nematodes
Root-knot nematode juveniles are active, thread-like
worms about 0.5 mm long - slightly too small to be seen
with the naked eye. These juveniles hatch from eggs, move
through the soil and invade roots near the root tip. They
occasionally develop into males, but usually become
spherical-shaped females. The presence of developing
nematodes in the root stimulates the surrounding tissues
to enlarge and produce the galls, which are typical of
infection by this nematode. Mature female nematodes
then lay hundreds of eggs on the root surface and these
eggs hatch in warm, moist soil to continue the life cycle.
The length of the life cycle depends on temperature and
varies from four to six weeks in summer, to 10 to 15 weeks
in winter.
If removing affected orchards and vineyards, do not
replant for at least one year. During this time, grow
green manure cover crops that are not hosts of root-
knot nematode. Examples are oats in winter and some
hybrids of sorghum
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sudan-grass during summer.
Where nematodes cause serious problems, prepare the
soil by ploughing deeply and then ripping and discing to
remove old tree roots.
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Apply an approved fumigant before replanting if
experience or population monitoring indicates that
nematodes are likely to be a problem.
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Nematodes are aquatic animals and require a water film
around soil particles before they can move. Nematode eggs
will not hatch unless there is sufficient moisture in the soil.
This means soil moisture conditions optimum for plant
Plant nematode-free stock.
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Use nematode-resistant rootstocks where available
(e.g. peach and grape).
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