Plant Pathology: Extension: Plant Disease Library

Lesion Nematodes

Lesion nematodes, Pratylenchus spp., are widespread with three major species found in Georgia. These nematodes cause root damage to a wide range of plants but they are not considered a major problem on most crops. Lesion nematodes enter roots and spend most of their lives inside root tissue. As females burrow through the root tissue, they lay eggs and the nematode population builds up inside the root. As lesions develop and expand at the damaged site, nematodes may leave the decaying tissue and move through the soil to find healthy root tissue on which to feed. Root injury results from penetration, feeding, and migration within the root. Fungi and bacteria frequently invade the roots through these wounds and cause small, brown lesions which may gradually enlarge, resulting in extensive root rot damage.

Lesion nematodes reproduce more slowly than many other nematodes. They typically begin reproduction six to eight weeks after they hatch. Eggs are laid singly rather than in a mass. Eggs and larvae overwinter well inside the roots of host plants where they are somewhat protected from the environment. During periods of drought, lesion nematodes in the soil may become quiescent. The nematodes will resume their activity when moisture increases and plants resume growth.

Lesion nematodes have been associated with root rot of many plants, particularly peanuts, tobacco, woody ornamentals, and strawberries. Other Georgia crops that support lesion nematode populations are corn, soybeans, alfalfa, clover, cowpeas, oats, okra, pepper, sweet potatoes, and vetch. Crop rotation is not usually effective in controlling this nematode because of its wide host range, including weed hosts such as crabgrass. Control with nematicides is not always successful. Fallow can be effective only if all host plants, including weeds, are prevented from growing during the fallow period.

Richard F. Davis, Extension Nematology, University of Georgia