Although root knot nematodes have a rather wide host range,
they frequently present problems on tomatoes, peppers
and okra in home gardens.
  Galveston County Master Gardener Sam Scarcella (Class of 1986)
planted his tomatoes on February 4, 2004 and the above photo
was taken on March 20, 2004! He is our expert on tomatoes.

A. Root knot nematodes are serious pests that live in the soil. They are small eel-like worms that feed within the plant root tissue. Female root knot nematodes produce large, rough galls on the roots of infected plants. The plant galls are formed in response to the nematodes’ feeding. Plants will often become wilted and stressed under severe infestations.

Root knot nematodes live most of their life inside the plant root. It is impossible to observe an individual nematode without a microscope or good quality hand lens. Only their damage can be readily seen with the naked eye.

Most often nematode feeding reduces the flow of water and nutrients into the plant roots, increasing the plant's susceptibility to other stress factors such as heat, water and nutritional deficiencies.

Control of root knot nematodes is accomplished by soil solarization, best performed during the summer months. Till up the soil, cover with clear plastic and seal around the edges. This is left in place for at least six weeks. Soil solarization is less damaging to beneficial soil organisms than chemical intervention.

Drying out the soil during the summer months is another method to reduce root knot nematodes. Rototilling or spading the soil helps remove soil moisture more quickly and exposes the nematodes and their eggs to the hot sun. Nematodes require moisture to survive.

Crop rotation also helps reduce nematodes in the soil. Do not plant the same crop in the same place from season to season. Remove and burn or bag infested plants. Planting French marigolds in infested soil is another natural control method that can be of some benefit in managing root knot nematode populations.

Although root knot nematodes have a rather wide host range, they frequently present problems on tomatoes, peppers and okra in home gardens. An effective procedure to managing root knot nematode infestations is to carefully dig up as much of the root tissue as possible, then remove excess soil and dispose of infested root tissue through household garbage. Be sure to not place infested root tissue in the compost pile.

There are numerous varieties of tomatoes and peppers that are resistant to attach by root knot nematodes. For instance, tomato varieties identified with the letter symbols "VFN" have genetic resistance to verticillium wilt (V), fusarium wilt (F) and root knot nematodes (N).

Vapam once was an effective chemical means of control but it is no longer available.


This web site is maintained by Master Gardener Laura Bellmore under the direction of William M. Johnson, Ph.D., County Extension Agent-Horticulture & Master Gardener Program Coordinator.

All digital photographs are the property of  the Galveston County Master Gardener Association, Inc. (GCMGA) © 2002-2013 GCMGA - All Rights Reserved.