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Root knot nematode

Scientific name: Meloidogyne spp.
Synonym: Root knot eelworm

Host

A wide variety of agricultural crops and weeds

Affected plant stages

All growth stages

Affected plant parts

Roots, leaves, the whole plant

Symptoms

Infected plants have swollen, impaired roots. Nematode's feeding stimulates the production of galls (root knots). Galls are found on the root system both on the primary and secondary roots. Their sizes vary from .02 to 20 cm in diameter.

The gall is characterized by smaller swellings and more uniformly distributed infection on the lateral feeding roots. Inside the gall are shiny white bodies of the female nematodes (about the size of a pinhead). At the root surface, shiny white to yellow egg masses are found. A closer look with a magnifier may show the adults, but mostly they are not seen with the naked eye.

Severe infestation results in stunted growth, yellowing of leaves, wilting, and poor yield because the galls disturb the roots ability to absorb water and nutrients. They also serve as openings for pathogens, such as fungi and bacteria, which cause plant diseases.

Factors that favor development

  1. Infected plant debris that are left on the field.
  2. Monocropping.
  3. Weedy field.
  4. Warm temperature and moist but well-aerated sandy soil.

Prevention and control

  1. Crop rotation.
    Broccoli, cauliflower, sorghum, Sudan grass, rape, and mustard seed are resistant to nematodes (Dofour; Guerena; Earles, 2003)
  2. Fallowing
  3. Deep plowing
  4. Use of resistant cultivars
  5. Use of organic fertilizer particularly the chicken dung
  6. Grow healthy plants
  7. Regular and timely weeding
  8. Plant French marigold (Tagetes patula). Planting distance is 17.5 x 17.5 cm in between hills and rows. Two months after, plow them under (Vann; Kirkpatrick; Cartwright, 2004). African marigold (T. minuta) plowed under the soil also reduces nematodes on tomatoes ( Dofour; Guerena; Earles, 2003)
  9. Basil extract
  10. Garlic extract
  11. Neem seed extract
  12. Pongam cake



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