Root-Knot Nematodes

Root-knot nematodes are the most economically important group of plant-parasitic nematodes, attacking over 3,000 plant species worldwide. They cause distinctive galls (knots) on roots that disrupt water and nutrient uptake, causing stunting, wilting, and yield loss. Meloidogyne species are particularly devastating in tropical and subtropical sandy soils where populations build up rapidly.

Microscopic worms (0.5-1 mm) — not visible to the naked eye. Diagnosis is based on root symptoms: distinctive round swellings (galls/knots) on roots. Dissecting a gall reveals pear-shaped adult females filled with eggs. Soil analysis (Baermann funnel method) quantifies juvenile populations.

• 1

  Dig up roots of stunted or wilting plants and examine for galls — round swellings on roots are diagnostic

• 2

  Galls from Meloidogyne cannot be rubbed off (they are integral root tissue), unlike nitrogen-fixing nodules on legumes which detach easily

• 3

  Affected plants often occur in patches corresponding to soil type (sandy spots have worse infestations)

• 4

  Submit soil and root samples to a nematology lab for definitive species identification and population counts

• 5

  Mid-season soil sampling from the root zone (top 20 cm) gives best population estimates

• Round, swollen galls (knots) on roots — the diagnostic symptom

• Stunted, chlorotic plants in irregular patches in the field

• Wilting during midday heat despite adequate soil moisture

• Poor response to fertilizer application

• Root system reduced and distorted with swollen galls

• Secondary root rot organisms colonizing galled tissue

Root-Knot Nematodes can attack 10 crop species.