| Columbia root knot nematode |
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| Meloidogyne chitwoodii |
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Plant hosts
- Major hosts: Daucus carota (carrot), Lycopersicon esculentum (tomato), Medicago sativa (lucerne), Solanum tuberosum (potato)
- Minor hosts: Chenopodium quinoa (quinoa), Phaseolus vulgaris (common bean), Pisum sativum (pea), Scorzonera hispanica (oyster plant), Zea mays (maize)
- Associated with: Avena sativa (oats), Beta vulgaris var. saccharifera (sugarbeet), Hordeum vulgare (barley), Poaceae (grasses), Triticum aestivum (wheat)
To view larger image click on picture.
Image provided by Clemson University USDA Cooperative Extension Slide Series.
Means of movement and dispersal
Plant parts liable to carry the pest in trade and transport:
- Growing medium accompanying plants: eggs, juveniles, and adults are born externally and visible under light microscope.
- Seedlings and micropropagated plants: eggs, juveniles, and adults are born internally and externally. This nematode is visible under light microscope.
- Roots: eggs, juveniles, and adults are born internally and externally. This nematode is visible under light microscope.
Plant parts not known to carry the pest in trade and transport:
- Bark.
- Bulbs,tubers, corms and rhizomes.
- Fruits.
- Flowers.
- Leaves.
- Stems.
- Seeds.
- Wood.
Transport pathways for long distance movement:
- Conveyances (transport Vehicles): eggs in soil.
- Containers And Packing: eggs in soil.
- Soil, gravel, water, etc.: eggs in soil.
- Travelers and baggage: eggs in soil.
Symptoms
Symptoms of M. chitwoodii vary according to host, population density of the nematode and environmental conditions. Above ground symptoms are often not obvious but may consist of varying degrees of stunting, lack of vigour and a tendency to wilt under moisture stress, all leading to reduced yield. The galls produced on potato tubers by M. chitwoodii differ from those caused by other species of Meloidogyne. M. hapla, for example, forms small but distinct galls (together with extensive root proliferation) while M. incognita forms large, easily noticeable galls. The symptoms caused by M. chitwoodii are often not easily detected and are more apparent in some cultivars than in others; tubers may, in some cases, be heavily infected without visible symptoms. When present, the galls appear as small raised swellings on the tuber surface above the developing nematodes. A number of galls may be concentrated on one area of the tuber or single galls may be scattered near eyes or lesions. Internal tissue below the gall is necrotic and brownish. Adult females are visible just below the surface as glistening, white, pear-shaped bodies surrounded by a brownish layer of host tissue. Potato roots may also be infected, but this is difficult to detect without a magnifying lens, as little or no galling occurs, even in heavy infestations. The spherical bodies of females may protrude from the surface of small rootlets surrounded posteriorly by a large egg-filled sac which becomes dark-brown with age.In other crops, root galls and reduced root production decrease yields and marketability. Gall formation occurs on most cereals but is more noticeable on wheat and oats than on barley or maize. In tomatoes, M. chitwoodii produces root galls in some cultivars but not in others.
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