root wilt disease – Coconut is one of the largest horticultural crops in peninsular India, and an increasing number of farmers are taking up coconut plantations due to a lack of labour availability and the intensive attention required to raise annual crops. The three States of Karnataka, Tamil Nadu, and Kerala together account for about 82-83 % of India’s coconut production.
Coconut is not only culturally interwoven but also defines the landscape of regions like Alappuzha and Pollachi, known for their pristine beauty. Now, this carefully cultivated imagery is under threat from a microscopic adversary: phytoplasma. Specifically, phytoplasma-induced root wilt disease has destroyed large tracts of traditional coconut-growing areas in these three States.
Rapid expansion Root wilt disease is a debilitating condition. It is classified as a non-fatal disease and was first identified more than a century and a half ago in Erattupetta in Kerala. More than 150 years of sustained scientific research at the Central Plantation Crops Research Institute (CPCRI), Kayamkulam, has yet to yield a definitive cure.
The disease spreads through insect vectors, aided by the movement of wind and uninterrupted stretches of coconut plantations. While the disease has existed for decades, its spread used to be limited. Today, its rapid expansion has caught many farmers unprepared.
In fact both farmers and the scientific community concur that erratic temperatures, especially extremes, and the rise of new sucking pests, particularly whiteflies, have significantly accelerated its spread. The combined effect of abiotic stress induced by climate change and biotic stress from emerging pests has rendered coconut palms increasingly susceptible to root wilt disease.
Once a few palms are infected in a region, sufficient inoculum builds up to hasten further spread. Recent assessments indicate that more than 30 lakh coconut palms have already been affected across major coconut-growing regions. In areas such as Pollachi, where farmers have prospered by adopting intercropping systems in coconut plantations with shade-loving permanent crops like cocoa and nutmeg, the situation has turned into a double disaster.
Without the shade of the coconut canopy, cocoa and nutmeg trees simply succumb to thermal stress. A successful tool Research institutions have attempted to address this plight through two broad approaches: first by developing standardised integrated cultivation practices using a judicious mix of organic and inorganic inputs, and second by developing resistant and tolerant varieties. Farmers who have religiously followed the recommended practices contend that these measures have done little to prevent the spread of the disease.
Once a tree is infested, symptoms appear only after a prolonged incubation period, and often vary, since they are superimposed with those of other diseases such as leaf decay. The tree quickly becomes unproductive, sheds all its nuts, and assumes a distorted appearance. Even if the disease is not immediately fatal, the palm continues to act as a source of pathogen inoculum.
The phytoplasma challenge is not confined to coconut alone. The spread of yellow leaf disease in arecanut across parts of Karnataka serves as a parallel reminder of how vector-borne palm diseases can silently expand when early, field-based interventions are inadequate.
CPCRI Kayamkulam has released one resistant and three tolerant varieties. Institutions such as the Tamil Nadu Agricultural University and the Coconut Development Board (CDB) multiply these varieties, but production has been limited to only a few thousand seedlings a year.
Breeding resistant and tolerant varieties remains one of the most successful tools for managing phytoplasma, as demonstrated by the high degree of success in addressing phytoplasma-related diseases in palms across the globe, from the Caribbean to Africa. Steps can be taken to import such varieties under strict quarantine protocols for field evaluation.
Participatory approach However, a more prudent and sustainable approach would be to tap into the reservoir of genetic wealth already standing in farmers’ fields within highly infested endemic zones. Coconut palms that display tolerance under high inoculum pressure and intense vector load hold the key to combating phytoplasma.
A participatory approach to selection offers a credible pathway to addressing the central constraint in combating phytoplasma: identifying and breeding resistant and tolerant varieties. In highly infested regions, systematic participatory selection of coconut palms, combined with structured observation, can be undertaken with farmers playing a central role. With appropriate training, farmers can be enabled to identify potentially tolerant palms and can be instructed on the importance of careful, long-term observation and record-keeping.
This would significantly reduce the burden on scientific institutions while generating richer, field-relevant datasets. Once tolerant or resistant palms are identified and validated, they can be inducted into decentralised breeding programmes, allowing multiple small, independent selection and evaluation efforts to proceed simultaneously under scientific supervision. Such an approach also enables the isolation of locally adapted varieties suited to specific agro-climatic conditions.
Institutional action Given the rapid expansion of root wilt disease into new frontiers, mirroring the trajectory of whitefly, which was once confined to a few pockets in western Tamil Nadu but is now a pan-India pest, time is of the essence. Farmers whose palms are selected for breeding can also benefit through royalty mechanisms envisioned under the Protection of Plant Varieties and Farmers’ Rights Act while being encouraged to establish nurseries to multiply planting material at scale to replace the vast number of palms being felled.
The government and the scientific community must, therefore, place renewed faith in citizen science and ensure that participatory selection and participatory breeding are pursued in all earnestness to confront the phytoplasma menace threatening coconut cultivation. Addressing root wilt at this scale requires coordinated institutional action. Central agencies such as CPCRI and the CDB must work closely with the agricultural universities of Kerala, Tamil Nadu, and Karnataka.
Fragmented research efforts and parallel trials no longer suffice in the face of a fast-spreading phytoplasma threat. A shared framework for data, evaluation, and field validation is essential to translate participatory science into impact.
R. Ranjit Kumar is managing director, Pollachi Nutmeg Farmer Producer Company, and ICAR-IARI Innovative Farmer Awardee.