Nematodes in the home garden
Department of Primary Industries and Fisheries.
Root-knot nematode (Meloidogyne spp.) commonly causes swellings or
galls on the roots and other underground parts of many plants grown in the home
garden. The galls, which can vary from 1 mm to several centimetres in diameter,
reduce the efficiency of the root system so that affected plants are stunted and
unthrifty.
Hundreds of plant species are susceptible to root-knot nematode, but it most commonly causes damage on the following crops:
|
bean beetroot begonia carrot carnation coleus cucumber |
celery eggfruit grape kiwifruit papaw pea peach |
potato pumpkin radish rose silverbeet tomato watermelon |
Life cycle
Root-knot nematode juveniles are active, thread-like worms about 1/2 mm long and 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 is temperature dependent and varies from 4-6 weeks in summer to 10-15 weeks in winter. Nematode multiplication and the degree of damage is therefore greatest on crops grown during the warmest months of the year.
Control
Destruction of infected roots
Immediately after a crop is harvested, roots of infected plants should be dug out and destroyed. This removes a large proportion of the nematodes which would otherwise carry over until the following season.
Fallowing
Continuous cropping with susceptible crops soon causes nematode numbers to increase to damaging levels. However, populations decline when moist soil is fallowed. Since root-knot nematode can increase on most weeds, they should be removed by cultivating the soil every 2-3 weeks. Cultivation also brings soil to the surface so that nematodes are exposed to the lethal heating and drying effects of the sun.
Rotation with marigolds
Most varieties of French marigold (Tagetes patula), especially Petite Harmony and Petite Yellow, are resistant to root-knot nematode because their roots secrete nematicidal chemicals. This phenomenon can be utilised for nematode control by dividing a vegetable garden into strips or blocks and planting marigolds in some part of the garden each year. Since a complete cover of marigolds is required, seed or seedlings should be planted no more than 15 cm apart and weeds should be kept under control until the marigold canopy crowds out competing weeds. After flowering, seed-bearing heads are removed to provide seed for the following crop and to reduce annoying volunteers that will be weeds in the succeeding vegetable crop. The marigolds are then incorporated into the soil with a spade or rotary hoe.
Use of tolerant crops
In areas where severe nematode damage has been experienced, it may be possible to grow crops of sweet corn, strawberry, capsicum, cabbage or cauliflower, as these crops tend to be resistant or tolerant to some species of root-knot nematode.
Care of the host plant
The effects of nematodes can be off-set to some degree by protecting plants from stress. Regular water and fertiliser, the use of mulch, and the control of diseases caused by other organisms tend to reduce the damage caused by nematodes.
Organic manures
The addition of large amounts of organic matter (compost, lawn clippings, animal manures, etc.) to soil is known to be beneficial to plants and detrimental to nematodes. Organic amendments should be incorporated into soil well before planting and crops should not be planted until decomposition is complete.
Further information
- NemaSYS
Information contained in this publication is provided as general advice only. For application to specific circumstances, professional advice should be sought. The Department of Primary Industries and Fisheries, Queensland has taken all reasonable steps to ensure the information in this publication is accurate at the time of publication. Readers should ensure that they make appropriate inquiries to determine whether new information is available on the particular subject matter.
Last updated 04 February 2004
