Plant Parasitic Nematodes: An Invisible Threat to Sustainability in Spices

Biotic stresses, like fungi, nematodes, and disease complexes, and abiotic stresses like extreme temperatures and deficient or excessive water are serious threats to the productivity of spice plants. Plant parasitic nematodes are soil-dwelling parasitic worms that feed on the roots of crops, causing yield losses and also contribute to the susceptibility of the plants to invasion by other pathogens. A wide variety of nematode species are identified as parasites of spices. Among these, root knot nematodes are unique as they infect almost all spice crops. Some species of burrowing and lesion nematodes are also known to parasitize spices. Meloidogyne spp. are the most widespread and damaging genus of plant parasitic nematodes infecting spices. Plant parasitic nematodes, like Pratylenchus and Radopholus, play a significant role in diseases like slow decline of black pepper, ginger yellows disease, and dry rot of turmeric. Nematode control is a difficult task today due to the non-availability of chemical pesticides that are less harmful to the environment. In spices, there is a great scope for sustainable management measures like using nematode-free planting material, resistant varieties, soil amendments, and bio-nematicides or botanicals. Nematode-free planting materials can be very effective in vegetatively propagated spice crops like black pepper, cardamom, ginger, and turmeric. For this, the thrust should be on zero tolerance to plant parasitic nematodes in spice nurseries which can be achieved by employing modern diagnostic tools, nursery certification, and eradication through effective pesticides. On the other hand, plant parasitic nematodes can be managed in fields by integrating various eco-friendly methods. There is a very wide scope for isolating more efficient biocontrol agents effective against nematodes. Developing resistant lines is another thrust area in spices as India possesses rich genetic resources of most of these crops. Modern biotechnology tools will be of immense use for achieving rapid successes in this field.