French Marigolds Tagetes patula

How to Control Root Knot Nematodes

How to Control Root Knot Nematodes in Your Home Garden

French Marigolds Tagetes patulaRoot-knot nematodes (Meloidogyne spp) are parasitic roundworms which can damage vegetable, fruit, and ornamental plants. These nematodes cause swellings in the roots which will result in stunted growth, wilting or death of the plant. The infected plants are more susceptible to fungal and bacterial attack as well. Treating nematode infections in plants is difficult and hence prevention of infection is the right option. The important methods to control the infection of root-knot nematodes in your garden are discussed here.

Nematode Cover

The natural way to protect your garden plants from nematode is to plant nematode cover plants before planting the garden plants. These cover plants release substances which are toxic to nematodes and hence repels nematodes. Growing plants which are resistant to nematodes will reduce the ability of nematodes to feed and reproduce in the soil. This will result in the lower number of nematodes in the soil while growing garden plants susceptible to nematodes. The painted daisy (Chrysanthemum coccineum) and French marigold (Tagetes patula) are highly effective as nematode repellent cover plants for carrots and other vegetables. Space the cover plants about seven inches apart and allow them to grow for about two months. After two months or before the flower heads form the seeds, mix the plant in the soil. This will improve the toxic substance content in the soil for nematodes.

Planting Resistant Varieties

There are vegetable and fruit plants which are resistant to nematodes causing root–knots. Planting resistant varieties in the garden can ensure good crop even when nematodes are present in the soil. Nematode-resistant varieties of beans, peas, red and green peppers, tomato, etc., are available at the garden centres or at the online stores. This method will be more effective if combined with crop rotation or nematode cover plants. Make sure that the same type of vegetable plants or fruits is not grown in the same site every season.


Crop rotation is the practice of growing different varieties of plants in a site each year. Planting nematode susceptible plants in a new location in your garden each year ensures that they are not attacked by the parasites. Succession planting or growing nematode susceptible and nematode resistant varieties in alternate seasons are also effective.

Solarising the Soil

Root-knot nematodes need moist soil conditions for their growth, movement, and reproduction. Removing the roots of plants from the soil after each season and tilling the soil for two to three times before planting seedlings in the garden bed is very effective in controlling nematode growth in the soil. Tilling exposes any plant roots in the soil and will get dried by the sun. This will reduce the chance of nematode growth in the soil. Exposing the soil to sun or solarisation eliminate the pests and weeds in the soil. Gardeners can use thin and transparent plastic sheets to cover the soil and to increase the soil temperature in order to destroy any nematodes and other pests in the soil. It is ideal to raise the temperature to 120 F for better results.

Green Manure

Some plants which are used as green manures can kill nematodes present in the soil. Painted daisy, castor bean, ornamental crotalaria, and rapeseed can be used as green manure to kill nematodes in the soil.



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