Root-Lesion Nematode of Alfalfa
There are many species of root-lesion nematodes (RLN) that injure alfalfa, but Pratylenchus penetrans is considered the most important. High populations of RLN can decrease yield and cold tolerance and cause seedling death. Aboveground symptoms appear in patches or throughout a field as yellow, stunted plants. Roots have dark colored lesions and reduced lateral root growth. Lesions can coalesce and roots will rot. Other soilborne pathogens can enter roots via tissue injury caused by RLN, and RLN can “break” alfalfa cultivar resistance to these organisms.
Juvenile and adult RLN infect alfalfa roots, preferring the feeder roots where concentrated root hair growth occurs. Nematodes are often more problematic in fields with sandy or sandy loam soils.
Root-lesion nematodes are best managed by planting resistant alfalfa cultivars. Reduce RLN spread from infested to non infested fields by limiting soil movement on farm equipment or through irrigation water. Reduce RLN populations by either delaying seeding or applying a nematicide, following field fallowing. Manage weeds to reduce alternative RLN hosts.
Prepared and reviewed by the Alfalfa Pest Management Working Group.
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