Root-Knot Nematodes

Nematodes are microscopic roundworms that feed on plant roots, and root-knot nematodes (Meloidogyne spp.) are the most damaging group in turfgrass. They are terrifying because the damage is invisible until it is catastrophic — by the time you see above-ground symptoms, the root system has already been devastated.

We encountered a textbook nematode case on a three-acre Zoysia lawn that looked amazing all summer long. The lawn was put to bed correctly going into fall, went uniformly brown for dormancy — and the following May, roughly thirty percent of the lawn simply did not wake up. It stayed brown. The customer wanted us to re-sod the dead areas at an estimated cost of sixty thousand dollars.

Instead of sodding, we ordered a nematode assay from the University of Tennessee. The test confirmed root-knot nematodes in the soil. That sixty-dollar test saved sixty thousand dollars — because re-sodding over nematode-infested soil would have been pointless. The new sod roots would have been attacked immediately, and the same die-off would have repeated the following year.

Nematode damage is one of the reasons we specialize in fescue and do not currently service Zoysia or Bermuda lawns. Warm-season grasses in Middle Tennessee are susceptible to nematodes, chinch bugs, and large patch on top of the same fungal diseases that affect fescue — the liability and complexity of managing those additional pest pressures is significant.

If you have a warm-season lawn (Zoysia or Bermuda) and large sections fail to green up in spring after an otherwise healthy-looking fall, request a nematode assay from the University of Tennessee Extension before spending money on sod or seed. The test is inexpensive and can save you from a very costly mistake.

For fescue lawns, nematode damage is rare but not impossible. The standard grub and insect control program does not address nematodes — they require different diagnostic and treatment approaches.