Nematodes, other than root knot, which commonly cause plant injury are Helicotylenchus spp., Hoplolaimus spp., Heterodera spp., Globodera spp., Tylenchorhynchus spp., Xiphenema spp., Trichodorus spp., Longidorus spp., Belonolaimus spp., Rotylenchulus spp., Paratylenchus spp., Punctodera sp., and Paratrichodorus spp.
Except for Heterodera spp. and Rotylenchulus spp., most are of the migratory type. That is, they are mobile in the soil and move from feeding site to feeding site on the host plant.
When crops show slow decline, unthriftiness, chlorosis or slower than normal growth, nematodes, other than root knot, may be the cause. During periods of stress, infested plants will tend to wilt first. Other symptoms include a crooked or brushy appearance of fleshy tap roots, stubby, small root systems with excessive branching; small roots larger near the tip; brownish to black spots or streaks on roots. In many instances, nematodes occur as part of a fungal or bacterial disease complex. Plants attacked by nematodes are more susceptible to other unfavorable environmental conditions such as drouth injury, winter injury or excessive moisture.
Plant parasitic nematodes are microscopic in size which explains why they are often overlooked as causal agents. In addition, the above ground symptoms are typical of a large number of infectious and non-infectious root diseases. Nematodes live on the thin film of water that surrounds each soil particle and are, thus, very sensitive to dry soil conditions. Nematodes move very slowly in the soil but are moved in running water or contaminated equipment. If nematodes are suspected in an area, submit a soil sample to the Texas Plant Disease Diagnostic Laboratory. Control methods are the same as for root knot.