Sandy hillside infected with root knot nematode.
Galls produced by root knot nematodes in melon.
Wilting caused by root knot nematode in melon. (Courtesy: Dr. Richard Latin)
Root knot nematode (Meloidogyne incognita) is the most destructive plant parasitic nematode in melon growing areas of central Indiana. Plants infected with this nematode can wilt in middle of the day with no apparent reason, especially on hillsides with sandy soils. Plants might become yellow and stunted. Roots of infected plants swell and produce large galls all over the roots. White female nematodes are embedded inside these galls. Life cycles of these nematodes are similar to soybean cyst nematode except that they don't produce cysts. Second stage juveniles hatch from eggs in the soil and invade young seedlings in early spring. A second stage juvenile will establish a feeding site and go through several molting stages, swell and become a sedentary female encased within the root tissue that appears as galls. The life cycle of the RKN is about a month in optimum temperatures, 75-80°F. RKN is extremely hard to manage because of the wide host range. In addition to melon and many vegetables, RKN can infect corn and soybean as well. Soybean is a more susceptible host than is corn. Rotation is not as effective a management tool for this nematode because of its wide host range. Small grains and alfalfa can be used effectively as rotational crops. A few useful nematicides exist and might be cost effective to lessen RKN damage or increase yield in melon.