GALLS OR SWELLINGS ON ROOTS:

Root galls or knots are the most obvious root symptoms of any plant parasitic nematodes. Root knot nematodes cause root tissue growth and expansion around infection points that become visible on roots as swellings called galls or knots. The size of the gall depends on the host plant and the degree of infection. On some hosts, such as alfalfa, root knot nematode infection does not produce obvious root galling. Usually, galling is readily visible on infected roots of most common field and vegetable crops, and many perennial nut and tree fruit crops and vines. Several root knot nematode females may be found within a gall. Gall size will often depend on the number of nematodes that it contains. Gall abundance can indicate host susceptibility. On older, heavily infested roots, individual galls may become coalesced to provide uninterrupted swelling or galling along complete sections of a root. Meloidogyne hapla tends to produce smaller, more rounded galls on many host plants than do the other common root knot nematode species, although this alone is not a reliable means of identification.

Depending on the host plant, galling of the roots can be median; that is, along main portions of the root, or at the terminal or the ends of roots. An example of typical terminal root galling is M. naasi infection on barley and grasses. The false root knot nematode (Nacobbus) also produces large root galls, as on sugarbeet, and these may be easily mistaken for root knot galls.

From: McKenry, M.V. and P. A. Roberts. 1985. Phytonematology Study Guide. University of California, Division of Agriculture and Natural Resources. Publication 4045.

Other pests or conditions can cause root symptoms similar to root knot nematode damage. Dagger (Xiphinema), needle (Longidorus) and sheath (Hemicycliophora) nematodes also cause root galling. Nodules on the roots of legumes also bear a resemblance to root knot nematode galls.

Meloidogyne sp. on carrot
Meloidogyne sp. on carrots following late season infection of lenticels
Meloidogyne sp. on dahlia
Meloidogyne sp. on squash
Meloidogyne sp. on sugarbeet
Meloidogyne sp. on melon
Meloidogyne sp. on mulberry
Meloidogyne chitwoodi on potato
Meloidogyne naasi on barley
Meloidogyne sp. on tomato
Meloidogyne naasi on turf
Meloidogyne sp. cross section thru gall showing head of nematode on right surrounded by giant cells
Meloidogyne sp. on grape
Xiphinema index on grape
Xiphinema diversicaudatum on rose
Longidorus africanus on lettuce
Longidorus africanus on lettuce
Anguina on turf
Hemicycliophora galls on root tips of center plant

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