Feature Story
The SOUTHERN ROOT KNOT NEMATODE By Amy Dismukes, Nursery Extension Area Specialist, TSU, Otis L. Floyd Nursery Research Center
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lant parasitic nematodes are tiny, microscopic, “worm-like� animals (Fig. 1) that live in the soil and plant tissues. In Tennessee, the most troublesome species to the nursery industry are those that feed on plant roots and live in the soil. These nematodes can be challenging to diagnose, difficult to control, and can be easily spread from site to site in soil that may be carried on tools, on equipment and tires, on mud-caked boots, and within or on infested plant material. The Southern root knot nematode (RKN), Meloidogyne incognita, is a major pest in nurseries. RKN can infest the roots of many woody ornamentals including, but not limited to, boxwood (Buxus spp.) (Fig. 2), catalpa (Catalpa speciosa), cedar (Cedrus spp.), Japanese quince (Chaenomeles spp.), euonymus (Euonymus spp.), gingko (Ginkgo biloba), Althea (Hibiscus syriacus), hydrangea (Hydrangea macrophylla), Chinese holly (Ilex cornuta), jasmine (Jasmium primulinum), walnut (Juglans spp.), mulberry (Morus spp.), nandina (Nandina domestica), stone fruit (Prunus spp.), fire thorn (Pyracantha spp.), oak (Quercus spp.), and viburnum (Viburnum spp.). Root knot nematodes damage plant roots through their feeding activity, which is achieved by piercing root cells using a needle-like mouthpart called a stylet. Once attached to the root, feeding activity results in gall and clubbed-root formation on root tissues (Fig. 3).
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tennessee greentimes SPRING 2020
Fig. 1. Newly hatched (2nd stage) juvenile root knot nematodes (Photo Credit, Alan Windham)
Fig. 2. Field-grown boxwood shrubs infested by root knot nematodes may present symptoms similar to water stress or nutrient deficiency (Photo Credit, A. Dismukes)
