September 22, 2024 – As we move into this year’s fall season, it’s time to consider root knot nematode (RKN) protection for next year. RKNs are tiny roundworms living in the soil and common in your area. They penetrate tomato plant roots and feed on the nutrients. The results are knots ranging from tiny up to one-inch-thick, all of which interfere with nutrient transfers.
RKNs can only travel about one meter a year, so they stay in the same area, and they overwinter very well. Tomato plants attract them the first year, although damage is extremely difficult to see. Planting in the same spot the following year may result in some visible plant damage, with plant deaths likely the third year. While tomatoes are a prime target, RKNs can also attack peppers, okra, carrots and perhaps other vegetable plants. With the problem occurring beneath the soil, it’s difficult to spot damage early on, as leaf yellowing and perhaps stunted growth can be attributed to several causes.
Thankfully, there are a few ways you can handle an infestation, as well as a few more steps you can take to prevent root knot nematodes from ruining future crops. First, to control/reduce RKN populations, rotate your crops, hopefully on a 3–4 year scale. This can also help control other soil borne pests. This is extremely important if you have raised bed gardens. Tilling, by the way, spreads RKN populations.
Marigolds are a great RKN defensive plant, as their roots are toxic to, so plant a LOT of marigolds (NGT 12” apart), particularly French marigolds. They also provide protection from a host of other pests. Using non-leguminous cover crops in winter helps eliminating the food supply and prevents bare soil.
Finally, when purchasing tomato seeds check for VFN resistance on the label. The N stands for RKN.
