HPIPM:Root Lesion Nematode

Author: Howard F. Schwartz, David H. Gent, Gary D. Franc and Robert M. Harveson

Taxonomy

Domain	Eukarya
Kingdom	Animalia
Phylum	Nematoda
Class	Chromodorea
Order	Tylenchida
Family	Pratylenchidae

Scientific Name

Pratylenchus

Common Name

lesion nematode

Identification and Life Cycle

Many nematode species are found in association with dry bean roots. Two species that cause significant yield reductions are the root-knot (Meloidogyne spp.) and lesion (Pratylenchus spp.) nematodes. These species and the chrysanthemum foliar nematode, Aphelenchoides ritzemabosi, recently reported on bean in Wyoming, are discussed below. Root lesion nematodes reproduce most quickly and cause the most damage to dry bean in sandy soils. Damage is especially severe when soil moisture and nutrients are limiting. Their survival is best in cool, moist soils. Reproduction is highest at a soil pH of 5.2 to 6.4. The movement of infested soil on equipment, irrigation water, and the movement of infested plant material can disseminate nematodes within and among fields.

Plant Response and Damage

Root lesion nematode aboveground symptoms on plants with severe root infection may include chlorosis, stunting, and low vigor. Infected roots may be poorly developed and bear small, brown-black lesions. Small fibrous roots may be killed. Lesion nematodes are endoparasites, and their feeding and penetration activities may destroy epidermal and cortical cells. Root destruction is more severe in the presence of other soil-borne fungal pathogens which may mask the injury caused by lesion nematodes. Proof of lesion nematode infection requires extraction of nematodes from roots and associated soil, and identification of Pratylenchus spp.

Biological Control

Incorporation of green manure crops such as oat, sudangrass, sesame, rapeseed, white mustard, or perennial ryegrass the season before dry beans are planted can reduce some nematode populations.

Cultural Control

Control of lesion nematodes is based on practices that prevent populations from increasing to damaging levels. Crop rotation has limited effect because of the extensive host range of lesion nematodes. For example, very high populations are often found in roots of field corn. Many weed species support high populations of lesion nematodes and should be controlled throughout the crop rotation. There is limited information on availability of resistant varieties and resistance may vary significantly among the various species of lesion nematodes.

Chemical Control

Chemical nematicides may be effective but are expensive and may not be justified unless yield losses are high. Nematicides used on a previous crop in the rotation, i.e., sugar beet or potato, may exhibit some beneficial carryover effects on the following bean crop.

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