Tomato Grower's Guide: What are nematodes?

What is it?

Nematodes of many different species infect tomato plants. These nematodes are a microscopic worm which live in soil, however, they are not in any way related to the well-known earthworm. Some forms of nematodes are highly beneficial to tomato plants, while others can wreak total destruction on tomato plants in the garden. Tomato plant nematodes are prevalent throughout the United States, but they are most damaging to tomato plants in the Southern regions of the United States.

Tomato plant nematodes may have infested your garden if you note that the tomato plants are growing poorly and experiencing yellow on leaves and stems or stunted, distorted growth patterns throughout the plant. If you happen to look at the roots of your tomato plant, you will find that they have elongated growths which look like nodules throughout the root system. These evidences of tomato plant nematodes may be the only indication that they are present as even on close examination you are unlikely to view these microscopic worms.

How does it manifest?

Tomato plant nematodes prefer sandy loam soils that have lots of moisture. The good news is that on their own, these pests can only move a few inches each year. The bad news is that due to their micrsoscopic size, tomato plant nematodes are easily carried from their original infestation through rain, wind, soil, water or infested tools as well as transport on other items they come in contact with. Tomato plant nematodes feed on the plant roots which stunt growth and damage root systems. When the roots become damaged so that they can no longer provide sufficient nutrients for the growth of the tomato plant you will begin to see the yellowing and browning of the leaves and stem along with eventual die off of the entire tomato plant if left untreated. However, many problems of both soil and the root system can cause similar problems, so don’t just assume that you have tomato plant nematode infestation. Prior to diagnosing the problem as tomato plant nematodes, you will want to rule out conditions such as drought stress, poor soil structure, root rot, and soil deficiencies which can mimic the damage caused by tomato plant nematodes. Once you have ruled out other conditions as a cause, you should contact your local cooperative extension office to find out direction for sampling your soil as well as what testing laboratories to send the soil samples to. There will be a charge for these services, and although it is not usually that cost prohibitive, it’s best to rule out any other possible conditions before sending soil for sampling and testing..

What can you do about it?

The only method to absolutely confirm the presence of root nematodes is soil and root testing which can be done through your local cooperative extension office. The office should be able to provide you with information on how to take samples, and other necessary instruction such as the testing laboratories in your area to send them to. Unfortunately, even if tomato plant nematodes are the problem there are currently no chemical preparations available to the homeowner to kill them off in planted soil. However, even if you lose a plant or two, it’s good to be aware that you can prevent or at least control, tomato plant nematode infestation prior to planting by soil fumigation. Alternately, to avoid the problem all together you may wish to purchase and plant nematode resistant varieties of tomato plants. Commonly these are denoted by a capitol N after the tomato plant variety located on the seed packet or transplant identification tag.