Extension@YourService: Nematodes

First Posted: 8/29/2013

As the last days of summer wind down, you may be evaluating how your lawn or vegetable garden performed this growing season. If your grass is weak, or tomato plants unimpressive, you may want to determine if nematodes could be part of the problem. Nematodes are microscopic worms that live in the soil.

Some, though not all, nematode species are plant parasites. They feed on and damage plant roots. Being microscopic, nematodes are classified as a plant disease rather than as a pest. They are most prolific in sandy soils, and feed on the roots of everything from turfgrass to vegetables, depending on the species. Rootknot nematodes, for example, are particularly fond of tomatoes and okra, as well as other related vegetables, and though the worms are microscopic, the evidence of their presence is obvious. If your tomatoes are failing to thrive despite adequate water and fertilizer, pull up a plant and examine the roots. The roots of affected plants will be knotty and bumpy, as the nematode lives inside the root, feeds, and reproduces there. In addition to Rootknot nematode other plant pathogenic nematodes are Lance, Sting, and Soybean Cyst, just to name a few. Ring, Sting, and Spiral nematodes may cause problems in turfgrass.

If you suspect nematodes may be a problem, fall is the best time for testing. This is because nematode populations are highest in the fall. The North Carolina Department of Agriculture will perform nematode testing for just $3 per sample. Sampling for nematodes is similar to taking a soil test, though unlike a soil test you should place the soil sample in a plastic bag to avoid having the soil dry out, which will cause the nematodes to die before they can be detected in the lab. The Cooperative Extension office can provide the boxes and sample forms for the test.

Should lab results show you have nematodes, unfortunately there are no pesticides labeled for homeowner use to control them. For your vegetable garden, cultural practices such as using sufficient water and fertilizer, choosing resistant varieties, and rotating to non-host crops can help. Most important is creating a healthy, living soil ecosystem by adding organic matter such as compost to your soil, as this is one of the best ways to prevent the build up of nematode populations. An active, balanced soil ecosystem will have populations of fungi, bacteria, and beneficial nematodes, all of which act as competition and predators of plant parasitic nematodes, keeping their numbers under control. For turfgrass, the best approach is to ensure the lawn is receiving the proper fertility and water, and that the soil pH is correct for turfgrass needs. This will enable the grass to withstand the additional stress plant parasitic nematodes put on plants.

To find out more about managing and testing for nematodes, call or stop by the Cooperative Extension office.