Root-knot nematodes

Root-knot nematodes (Meloidogyne sp.) belong to the order Tylenchida and the family Meloidogynidae. These microscopic roundworms are among the most destructive plant-parasitic nematodes worldwide. They act as obligate parasites, living and feeding within the root tissues of their hosts, which causes severe disruption to plant growth and development.

The host range of these nematodes is vast, encompassing hundreds of plant species. Vegetables like tomatoes, cucumbers, peppers, and eggplants are particularly susceptible to severe infestations. In greenhouse environments, the controlled climate and constant food supply allow nematode populations to explode, often rendering the soil unsuitable for susceptible crops.

The life cycle begins with the second-stage juvenile (J2), which is the infective form that migrates through the soil toward root tips. Once inside the root, the nematode induces the formation of giant cells, which serve as a nutrient source. These cells stimulate the surrounding tissue to swell into distinct, knot-like galls. The female nematode remains sedentary within the gall, continuously producing eggs throughout the growing season.

The primary damage is caused by the disruption of the plant's root system. Galls inhibit the root's ability to uptake water and minerals effectively. Visible symptoms on tomatoes include stunted growth, chlorosis, and wilting during peak sunlight hours. Eventually, the damaged roots become necrotic and highly susceptible to secondary bacterial and fungal infections, which further accelerate the plant's decline.

• Rotate crops with non-host species or nematode-suppressive plants like marigolds or mustard.
• Implement soil solarization or steam sterilization in greenhouse conditions to reduce pathogen pressure.
• Select resistant tomato cultivars that carry specific resistance genes against Meloidogyne species.
• Incorporate biological control agents such as nematode-trapping fungi or antagonistic bacteria.
• Maintain high sanitation standards by removing and destroying all infected root systems after the harvest.