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Columbia root knot nematode
Meloidogyne chitwoodii

Plant hosts
Columbia root knot nematodes feed on 3,000 plant species including vegetables, legumes, cereals, grasses, bush and tree fruits, and herbaceous and woody ornamentals.

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. 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.
Image of root galls.
Image provided by Clemson University USDA Cooperative Extension Slide Series.

Columbia root knot nematodes are transmitted by the movement of infested soil, water, and plant material. Dirty farm machinery can transmit this pest from an infested field to a noninfested field. Infested propagation material such as cuttings and transplants can also transmit this pest.

Geographic distribution
Columbia root knot nematodes are distributed worldwide.

Applicable regulations
Columbia root knot nematodes are a pest of concern to Oregon's interstate and international customers.  Nematode testing is available through the Commodity Inspection Division.
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