Do I Have Nematodes?


Nematode damage in roots of a cotton plant
            Clemson Univ. USDA CES, Bugwood
A cotton field infested with nematodes commonly exhibits stunting, yellowed leaves, wilting and stress, which are caused by poor nutrition and lack of water. Nematodes trigger these symptoms by reducing the ability of the roots to uptake water and nutrients and stunting root growth.

Plant-parasitic nematodes use a hollow tube – known as a stylet – for feeding by puncturing root cells and withdrawing nutrition from the host plant. Additional symptoms can include an overall reduction in root mass, signs of galling on the roots, or distorted regions.

Above-ground symptoms

  • Severely infected plants may be stunted and may wilt under drought stress several days before noninfected plants
  • Height and size of the cotton is oftentimes reduced
  • Widespread irregular cotton plant growth
  • Chlorosis, or yellowing, is not pronounced, but plants often express nutrient deficiencies, especially nitrogen deficiency
  • Symptoms usually are first expressed in sandy areas of the field

Below-ground symptoms

  • Symptoms of some nematodes are difficult to detect as they don't cause distinct galls or swellings.
  • Root-knot-nematode infection of roots results in swellings, or galls, and reduced root mass
  • The galls are typically much smaller than those observed on hosts such as soybeans, okra or other vegetables.
    • Root galling results in reduced nutrient and water uptake, and premature drought stress leading to yield losses

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