Do I Have Nematodes?

Swellings in the roots of tomatoes are a symptom of root-knot nematodes.
                  University of California, Davis

Symptoms of damage caused by nematodes can be found both above ground and below ground. These symptoms can become more pronounced following an increased rate of ethylene production, which is common in infestations of root-knot nematodes. Symptoms such as stunting and a decline in fruit quality normally occur in patches of nonuniform growth, as opposed to a complete decline throughout an entire field.

Plant-parasitic nematodes use a hollow tube – known as a stylet – for feeding by puncturing root cells and withdrawing nutrition from the tomato plant. The timing of the effects of nematode feeding is based on nematode population, crop susceptibility and environmental conditions.

If a field is heavily infested with nematodes, tomato seedlings could fail to fully develop and the plant will suffer poor stand development. With less severe infestation levels, symptoms may be delayed to later in the growing season and become more pronounced as the season progresses.

Typical above-ground symptoms

  • Stunting
  • General unthriftiness
  • Premature wilting
  • Slow recovery to improved soil conditions
  • Leaf chlorosis, or yellowing
  • Various other symptoms common with nutrient deficiency

Common below-ground symptoms

  • Nematode infection of roots results in swellings, or galls, and reduced root mass
    • Root galling results in reduced nutrient and water uptake, and premature drought stress leading to yield losses
  • Tight mat of short, swollen roots
  • Dead roots

In addition to monitoring visual symptoms, collecting soil samples is an effective method to determine the presence of nematodes.