Nematode syn. Eelworm Control
© Frances Michaels
Nematodes are not insects but microscopic, long, thin worms, which is why a common name for them is eelworms.
This soil-borne pest causes stunted, unproductive plants. A common way to identify the problem is infected
plants will wilt rapidly in hot weather. When nematodes burrow into the roots they stimulate the development
of galls on the roots which become swollen, disfigured and knotty. Root knot nematodes infest a wide range
of plants, including roses, potatoes, carrots, tomatoes, cucumbers, lettuces and zucchini. The potato cyst
nematode Globodera rostochiensis
is very persistent in soils but luckily it is confined to a very
small area of Victoria and WA; these areas have been quarantined to prevent further spread.
Suggested Organic Strategies
- A healthy soil will have a range of microorganisms that are predators or parasites of nematodes. All
the usual ways of building a healthy soil such as adding adding compost, mulching and green manuring will
improve nematode control.
More information on soil improvement...
- A green manure can be grown
specifically for nematode control as there are plants that when chopped through the soil will decompose
and release a nematode killing gas; this process is known as bio-fumigation. Plants that contain high levels
of bio-fumigant compounds include: rapeseed (canola) Brassica napus,
marigolds and Indian mustard. BQ Mulch, canola
and mustard are cool season crops. Marigold
is a warm season crop that when mixed with
cowpea makes an effective, warm season,
nematode-controlling green manure.
- Practising crop rotation helps as when a non-host crop is grown for a season it can starve the existing
nematodes. Non-host plants include cowpea,
oats, wheat and
woolly pod vetch. A rotation
of 2 years or more between susceptible crops is needed to control a serious outbreak. Vegetable crops resistant
to nematodes include broccoli,
- Good hygiene will help limit the spread of this pest as nematodes cannot move quickly through the garden,
instead they are often spread on infected plants, muddy boots and garden tools.
- When harvesting infected plants, remove as much infected root from the soil as possible and dispose of
well away from garden areas. The infected roots can be used as mulch under native shrubs or trees but do not
place them in a compost heap, as it is unlikely to get hot enough to kill the nematodes.
- Solarisation can be a useful remedy for nematodes; it can also help combat stubborn weeds. To be effective
do this in summer and first water the soil well. Then cover the soil with clear 4mm thick plastic. Stretch
the plastic over the area, get it as close to the soil as possible. Bury the edges by digging a narrow
trench, tucking the plastic in and back-filling. The aim is to raise the temperature to between 45°C and 50°C
in the top 10 cm of soil. This is high enough to kill disease pathogens but most beneficial soil organisms
will survive. Leave the plastic in place for 4 to 6 weeks and then plant as usual.
- Digging fresh chicken manure into a hot, dry soil, something normally to be avoided, has been shown to
reduce nematode numbers.
- Drenching with water and molasses or sugar can also kill nematodes, but will have a negative impact on
Not all nematodes are a problem, a range of beneficial nematodes known as 'entomopathogenic' are used to
control plant pests.