Mitigation Strategies for Nematode Problems in India

5th March 2014, Thiruvanathapuram

Foliar nematode (Aphelenchoides besseyi) on tuberose flowers

The 18th biennial group meeting of the All India Coordinated Research Project (AICRP) on Plant Parasitic Nematodes (3-5th March, 2014) discussed various concerns and possible mitigation strategies on the problems of Nematodes in the country. The meeting was held under the chairmanship of Dr. Swapan Kumar Dutta, DDG, Crop Science, ICAR at Kerala Agriculture University. A book entitled ‘Root Knot Nematodes in India – a Comprehensive Monograph’ was released by the Chairman. The project has already documented nematode distribution in the country in the form of ‘Nematode Distribution Atlas’.

Experts were of the view that globalization and intense pressure on land due to increasing human population necessitated diversification of agriculture.  However, in the present scenario of agriculture production system, vagaries due to various biotic stresses have increased considerably due to intensification in agriculture.  Among these biotic stresses, plant parasitic nematodes have assumed alarming stature by their adverse effect on crop health, directly as pathogens as well as indirectly by pre-disposing the plants to fungal/  bacterial diseases and vectoring viruses. Annual losses due to plant parasitic nematodes are estimated to be around US $100 billion worldwide, while in India net loss due to nematode diseases has been pegged around US $40 million.

Cucumber roots infected with root knot nematode (Meloidogyne sp.)There is hardly any flora including cereals, ornamentals, fibers, oilseeds, pulses, vegetables, fruits etc that remained unaffected by these tiny hidden enemies which often remain ignored because of the lack of awareness and poor technical knowhow, microscopic nature, and non-specific symptoms. In particular, the root-knot nematodes (Meloidogyne spp.), migratory forms (Pratylenchus and Radopholus spp.) and cyst nematodes (Heterodera spp.) are the most devastating parasites. The problem in the sub-tropics and tropics is particularly severe, and many developing nations are seriously impacted in both food security and economics by these nematodes. Root knot nematodes have become one of the major detriments to crop production, especially under protected cultivation. The protected conditions in poly houses are congenial to growth and reproduction of nematodes.  Survey of 71 poly-houses, conducted showed 15 to be heavily infested with root-knot nematode rendering them unfit for cultivation unless drastic mitigation programme is constituted in place. Surveillance, monitoring and pest management assume more importance under protected cultivation.

Further expansion of infested areas, with potato cyst nematodes, Globodera rostochiensis and G. Pallida is a matter of concern. These nematodes of quarantine significance were earlier restricted to Nilgiri hills of Tamilnadu state. Nematode management is also hampered due to lack of a well-developed system of chemical management strategy.  Globally a well-known fumigant, Methyl bromide (MBr) is subjected to drastic restriction for field use due to environmental concerns. Carbofuran, only insecticide found effective against nematodes doesn’t have label claim for use against plant parasitic nematodes on a number of economically important crops.  Under such situation there is dire need to identify new molecules for nematode control or expand the label claims of existing insecticides that are having nematicidal properties. 

Fumigants like Dazomet (banned on tea in India), Metham Sodium, Sodium tetrathio carbonate etc., tested in small pots/ plots against nematodes may be considered for restricted application under expert supervision for control of potato cyst nematodes. International imports of seeds and bulbs due to stem and bulb nematode (Ditylenchus sp.); timber and furniture due to pine wood nematode (Bursaphelenchus sp.), should thoroughly be checked which are devastating and are of high quarantine importance for the country. A strategic plan with integration of regulatory approach and pragmatic research planning would be required to weed out the menace. Number of approaches including enforcement of  domestic quarantine, regulated interstate movement of infected vegetative propagules (like rooted plants, banana suckers, potato tubers, bulbs, paddy seedlings), identification of sources of resistance, determination of mechanisms of host resistance, breeding for resistance, development of novel molecules and biocontrol strategies, setting up of accredited bioagent production units to ensure quality products, identification of nematode genes essential to parasitism, feeding and reproduction and their RNAi-mediated gene silencing or identification of determinants of resistance in host for transgenic development. 

Researches on the basic, strategic and applied frontiers of nematodes would need proper planning and funding to develop robust strategies to keep hidden pests and losses caused by them under check.

(Source: Crop Science Division, ICAR)