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Ministry of Agriculture, Food and Rural Affairs

Nematodes

Nematode lesions on roots Root lesion nematode on roots Root knot nematodes symptoms on roots Nematodes
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Beginner

Scientific Names
Meloidogyne hapla (root knot nematode)
Pratylenchus spp. (root lesion nematode)

Identification

  • Microscopic, wormlike creatures that live in soil and feed on strawberry roots.
  • Symptoms include:
    • uneven plant growth,
    • poor stand establishment,
    • weakened plants,
    • poor root growth,
    • fewer fine feeder roots and a bushy appearance (root lesion nematode),
    • reddish-brown lesions on feeder roots (root lesion nematode),
    • swells or galls on feeder roots (root knot nematode).

Often Confused With
Other root and crown insects and diseases

Period of Activity
Nematodes feed and multiply on plant roots all through the growing season. Populations are usually highest in May-June and September-October.

Scouting Notes
Nematodes can be identified from soil sample, or from plant roots. The best time to sample soil in an annual crop is after the crop has died down and while the soil is still moist, in the fall or the spring.

Thresholds

NEMATODE THRESHOLD IN SOIL THRESHOLD IN ROOTS
Root lesion 500/ kg soil 50/ gram dry root
Root knot 1000/ kg soil None established

 

Advanced

Scientific Names
Meloidogyne hapla (root knot nematode)
Pratylenchus spp. (root lesion nematode)

In Ontario the root lesion nematode is the most common nematode pest. Occasionally root knot nematodes are present in strawberry fields.

Identification
Nematodes are microscopic, wormlike creatures that live in soil and feed on strawberry roots. They can cause stunted growth and make plants more susceptible to infection from Verticillium and other soil born diseases.

The major symptom of nematode problems are uneven growth, and gradual decline of plant vigour.

Root knot nematode symptoms:

  • Patches in the field with stunted, yellow older leaves.
  • Weak, wilted, or missing plants.
  • Small swellings or galls on roots.
  • Roots branch to form clumps of hairy roots above galls.
  • Deformed roots appear stunted, stubby and knobby.

Root lesion nematode symptoms:

  • Patches of wilted, stunted plants with yellow older leaves.
  • White roots with rusty red flecking and brown lesions.
  • Roots may have large brown-black lesions or the entire root system may be black and necrotic.
  • Secondary roots become necrotic with dry areas.
  • Weak, short secondary roots develop in response to damaged root tips, creating a brushy, or witches broom appearance to the root system.

Often Confused With
Other root and crown insects and diseases (Soil samples are required to verify a nematode infestation.)

Biology
Nematodes overwinter in the soil, in roots and in crop debris. When soil conditions become favourable, young nematodes migrate to the roots of host plants. Most nematodes live in the top 60 cm (2 ft.), but they may travel over a meter (3 ft.) in search of host roots. Once roots are found, nematodes begin feeding and disrupt the water and nutrient conducting vascular tissue, resulting in reduced plant growth and yield. Root knot nematodes stimulate root cells to enlarge and become galls. Root lesion nematodes move in and out of plant roots, depending on soil conditions while root knot nematodes remain in the root.

Period of Activity
Nematodes feed and multiply on plant roots all through the growing season. Populations are usually highest in May-June and September-October.

Scouting Notes
Nematode populations can be identified by sampling soil or plant roots; sample soil to predict a problem before planting, or sample plant roots to diagnose an existing problem.

Getting accurate counts from plant soil can be tricky because nematodes move in and out of plant roots, and up and down in the soil profile. The best time to sample soil in an annual crop is after the crop has died down and while the soil is still moist, in the fall or spring.

Thresholds

NEMATODE THRESHOLD IN SOIL THRESHOLD IN ROOTS
Root lesion 500/ kg soil 50/ gram dry root
Root knot 1000/ kg soil None established

Management Notes

  • Nematodes must be controlled before planting.
  • Always test soil for nematodes before planting berry crops if:
    • soil is sand or sandy loam,
    • berries have been grown for many years, or
    • field is an old orchard site.
  • Always purchase plants grown according to the guidelines of an accredited plant propagation program.
  • Inspect transplants for root swellings and tiny knots and never plant seedlings that appear to have symptoms of root knot damage on the roots.
  • Use fumigants or nematode-suppressing cover crops before planting to reduce nematode numbers.
  • Long periods of fallow have proven to reduce population levels but this is not always an economically viable solution.
  • For root knot nematode, reduce soil populations by growing grasses, cereals or corn which are not hosts of root knot nematode.