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S.
Sardanelli and F. Ellison
Nematology Series, NDRF Fact Sheet No.4 Revised September 2005 |
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· A worm-shaped, plant-parasitic animal.
· Nearly microscopic and invisible to the naked eye.
· One of the most economically damaging plant-parasitic nematodes because of it's wide host range and widespread distribution.
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| Light micrograph of three second-stage juveniles of root-knot nematode, Meloidogyne sp. (Eisenback) | Scanning electron micrograph of a second-stage root-knot nematode juvenile propped up against a human hair (Eisenback) |
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| Second-stage juveniles of root-knot nematode, Meloidogyne sp., penetrating the root-tip of tomato (Eisenback) |
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| Root-knot nematode female and egg mass of the root-knot nematode, Meloidogyne sp. (Eisenback) | Brown colored egg masses produced by females of the root-knot nematode, Meloidogyne on African violet (Viola sp.). (Zunke) |
· The female root-knot nematode lays her eggs on the outside of the roots.
Root-Knot Nematode Hosts
All major field crops, vegetable crops, turf, ornamentals, and legumes are
susceptible to one or more of the root knot species.
· Below ground symptoms are swollen or knotted roots (root galls) or a stubby root system.
· Root galls vary in size and shape depending on the type of plant, nematode population levels, and species of root-knot nematode present in the soil.
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| Root-knot nematode, Meloidogyne sp., infection on boxwood showing above ground symptoms (Lopez) | Galls caused by root-knot, Meloidogyne spp., on boxwood (Overstre) | Galled root system of tomato infected with root-knot nematode, Meloidogyne sp., compared with non-infected root system (Eisenback) |
Management
The following widely recognized Integrated Pest management (IPM) strategies
are critical to management of root-knot nematodes.
Prevention:
This strategy should be the first line of defense. Prevention is the practice
of keeping a population of nematodes from infesting a site and specific tactics
include:
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| Soil sampling for research and advisory service (Zunke) |
· Survey sampling of an intended planting site to determine the degree of existing nematode activity. See "Sampling Procedures" page
· Use of nematode free transplants.
· Careful examination of transplant roots before planting can prevent the introduction of nematodes that would attack present and future susceptible plantings.
· Controlling weeds, which can act as hosts to some species of root-knot nematode.
· Keep other pests under control.
· Sanitation practices such as cleaning of equipment between sites of operation.
Avoidance: practiced when nematode
populations exist in a site, but their impact can be avoided or lessened through
some cultural practice. Examples of avoidance tactics include:
· Sampling to determine nematode species and population levels.
See "Sampling Procedures"
page
· Choosing plant materials that are poor hosts.
· Practice crop rotations that include nonhost, resistant and susceptible
crops when feasible.
· Employ cultural practices known to be optimal for plant growth.
· Root barriers and container growing.
· Isolate/destroy plants that are known to be infested with root-knot
nematodes and replace infested soil.
Monitoring:
includes tracking and proper identification of nematodes and
includes:
· Soil and plant sampling for detection and trouble shooting.
· Routine sampling to maintain records of incidence and distribution.
These samples form the basis for crop rotations, cultivar selection, economic
thresholds, suppressive actions, and other management decisions.
Suppression:
nematode suppressive tactics may become necessary to avoid economic crop loss
where prevention and avoidance tactics are not successful.
Nematode Suppressive Crops -
Auburn University - http://www.aces.edu/pubs/docs/A/ANR-0856/
Suppressive tactics include:
· Cover crops and Green manures improve the fertility of the
soil. As the plant material decays, the nutrients are released into the soil
and are taken up by the subsequent crops planted in the soil. However, the
time that is required for the cover crops or green manures to fully decay
and penetrate to the root zone varies and can take up to an entire year. Both
cover crops and green manures increase the bacteria, fungi, and other microorganism
populations in the soil, which can aid in reducing root-knot numbers. When
a cover crop is tilled into the soil (turned in) it is then referred to as
a green manure.
· Soil amendments, such as compost and manure, and mulches with
high organic matter will increase the chances that root-knot antagonistic
organisms will develop.
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· Fallow period with no susceptible plants for a period of one to two years (in the area with high root-knot populations) can significantly reduce the population size.
· Resistant varieties can prevent root-knot nematode reproduction (reducing populations significantly), have no requirements for special application techniques or equipment (as in the case of chemical management), and have similar costs to non-resistant cultivars. They can be used in addition to other suppressive mechanisms such as crop rotation and soil amendments.
· Soil solarization uses the natural heat from the sun to reduce
nematode populations. Prior to planting, when the soil can receive the most
direct sunlight, it is covered with a plastic polyethylene tarp for four preferably
six weeks.
Chemical Management:
Chemical control involves the application of certain volatile (fumigants)
and nonvolatile nematicides to the soil to reduce nematode populations. Chemical
management reduces nematode populations for a limited period of time. Nematodes
that escape treatment can resume feeding when the chemical is gone.
Recommendations for the application of nematicides may be found in the University
of Maryland's current Extension publications.
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Related References:
· Barker, K.R., C.C. Carter and J.N. Sasser, Eds. 1985. An Advanced
Treatise on Meloidogyne: Volume II. North Carolina State University Graphics.
223 pages.
· Sasser, J.N. and C.C. Carter, Eds. 1985. An Advanced Treatise on
Meloidogyne: Volume I. North Carolina State University Graphics. 422 pages.
· Sasser, J.N. and M.F. Kirby. 1979. Crop Cultivars Resistant to Root-Knot
Nematodes, Meloidogyne species, With Information on Seed Sources. Dept. Plant
Pathol., N.C. State Univ., Raleigh, NC and USAID. 24 pages.
Helpful Websites:
· Parasites of Plants- An extensive database of individual nematode
species including host symptoms, management, characteristics, and references.
(http://www.mda.state.md.us/)
· Florida Cooperative Extension Service- (http://edis.ifas.ufl.edu/)
Contains information on pest management, extension resources, and an extensive
list of related web sites.
All pictures are courtesy of Nemapix Jounal of Nematological Images, vol.
1 &2, J.D. Eisenback & Ulrich Zunke, eds.
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