We are no strangers are to challenges in East Texas agriculture. Floods to drought and insects to diseases – all effect gardens, landscapes, and forage production alike. One of the most frustrating is caused by microscopic roundworms in the soil called root-knot nematodes.
Nematodes are not insects, so sprays or dusts won’t touch them. They attack plant roots, plugging them up and causing swelling and ‘knots’. The knots reduce water and nutrient uptake and the result is weak, stunted plants that never seem to thrive—no matter how much fertilizer or water you apply.
Now to be clear, there are numerous kinds of nematodes and only a few are harmful. It is the ‘root-knot’ nematodes that adversely affect plants by stunting their growth. The others that seem to go unnoticed can be quite beneficial.
According to Texas A&M AgriLife Extension, root-knot nematodes are widespread in our region and especially damaging in vegetable gardens and lawns. Crops such as tomatoes, okra, beans, squash, and cucumbers are common victims. Turfgrasses can also show thinning and yellowing when nematodes are present.
But these “invisible”, microscopic roundworms are not readily evident and are frequently blamed for poor plant performance. In many a garden, I’ve asked if I could pull up a plant and study the roots. Sacrificing a tomato plant, I’ll gently tug them out of the soil and study the roots, looking closely for the swollen ‘knots’. Study some pictures of infected plants and you will learn to easily identify them too.
So, what’s a gardener to do if you do find them? Experts recommend several cultural strategies. First, rotate crops when possible, avoiding planting susceptible vegetables in the same spot year after year. Next, choose resistant varieties where available. For example, some tomato varieties are labeled with “N” for nematode resistance. Lastly, improve soil health by incorporating organic matter to encourage beneficial microbes that naturally suppress nematodes.
Now unfortunately, once nematodes are in your soil, there is no quick, one-time fix. That’s where a unique method—called a trap crop—comes in. One of my favorite trap crops is Elbon rye.
This fall, purchase some cereal grain rye (making sure it is the Elbon rye variety) and sow it thick across your affected garden soil. Rye grain is a winter annual that germinates in the fall and, if left to fully mature, would make rye grain in the spring. (Please do not confuse this with ryegrass that is so common in some pastures and your local bar-ditch!)
Here’s how the trap works: Root-knot nematodes enter Elbon rye roots looking to do their work within their roots, but unlike with your tomatoes or squash, they cannot successfully reproduce. This interrupts their life cycle, the adults cannot leave, and reduces their overall population.
Not only is this variety of cereal rye a trap crop for nematodes, it also helps reduce erosion and adds organic matter when it is incorporated into the soil.
Timing is critical. Plant rye in the fall, allow it to grow through winter, and then shred and turn it under at least two to three weeks before spring planting. Allowing time for decomposition prevents rye residue from interfering with vegetables that follow.
Plant now till mid-October for the best stands, but know that it can be started as late as early November. Seed Elbon rye at a rate of 3–4 pounds per 1,000 square feet.
About one month before you plant in your garden, you must mow down your rye and incorporate the plant material into the soil. That may be mid-January for your potatoes or as late as mid-March for purple-hull peas.
Is this a silver bullet? No. But planting Elbon rye thick will certainly eliminate a large percentage of the nematodes present. Repeat plantings of Elbon rye over the years will continue to diminish their numbers.
Root-knot nematodes may be invisible, but their damage is easy to spot. While there’s no silver bullet, planting Elbon rye in the fall is a science-backed, sustainable way to chip away at populations and give your garden crops a healthier start in spring.
For more information on nematodes and recommended control practices, visit Texas A&M AgriLife Extension at aggie-horticulture.tamu.edu.
