Do I Have Nematodes?

Damage caused by nematodes is difficult to estimate because damage to roots may not be apparent in above-ground symptoms. Below are some descriptions of symptoms to help growers identify above-ground or below-ground nematode problems.

Above-ground symptoms

• Severely infected plants may be stunted and may wilt under drought stress several days prior to noninfected plants.
• 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

• Nematode infections of roots result in swellings, or galls.
• 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.
• The damage to the roots caused by nematodes provides an entry point for soil-borne diseases, such as black shank and Granville wilt.

In addition to monitoring visual symptoms, collecting soil samples is also an effective method to determine if you have nematodes.

Infestation Levels
To determine infestation levels of root-knot nematodes, examine the roots. First, observe the roots at random just after fall stalk and root destruction (immediately after harvest). You can estimate the infestation level by observing the galled area and using the following index:

Low infestation – 0 percent to 10 percent of root area covered with galls
Moderate infestation – 11 percent to 25 percent of root area covered with galls
High infestation – 26 percent to 50 percent of root area covered with galls
Very high infestation – 51 percent to 100 percent of root area covered with galls