Root-lesion nematodes

Root-lesion nematodes, scientifically known as Pratylenchus species, are migratory endoparasites that cause significant damage to the root systems of various plant species. Unlike other types of nematodes, they continuously move throughout the root cortex, feeding on cells and causing widespread tissue destruction as they migrate.

The host range is exceptionally diverse, encompassing hundreds of plant species, including grasses, vegetables, and fruit trees. Among perennial crops, the black walnut is particularly vulnerable, where heavy infestations lead to severe root decay, reduced vigor, and a gradual decline in the tree's health that can last for several years.

Diagnostic symptoms include the appearance of small, dark necrotic lesions on the roots, which often coalesce, leading to total root decay and stunted root growth. Above-ground, plants exhibit signs of nutrient deficiency, such as yellowing leaves (chlorosis), wilting during dry periods, and an overall reduction in vegetative growth and fruit yield.

These nematodes thrive in a variety of soil types, particularly where there is sufficient moisture for movement through soil pores. They are highly resilient and can persist in the soil for long periods, surviving in root debris or in the soil matrix. They spread primarily via movement of infested soil, farm equipment, or infected rootstocks during transplanting.

Integrated management is essential for effective control of root-lesion nematodes. This includes the use of certified nematode-free planting materials, implementing long-term crop rotation schemes using antagonistic crops, and improving soil health through organic amendments. In severe cases, chemical nematicides may be necessary, though they should be used as part of a broader soil health program.