Deadly Fungus Threatens Critically Endangered Tree in the Western Ghats

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A newly emerging fungal disease is endangering Dipterocarpus bourdillonii, a critically endangered tree species found only in the Western Ghats of Kerala. Researchers have identified Corynespora cassiicola, an aggressive fungal pathogen known for its broad host range, as the cause of a fast-spreading leaf spot and blight disease. This alarming discovery has prompted scientists to call for immediate conservation and disease-management measures to save one of India’s most ecologically valuable trees.

An Endangered Giant of the Rainforest

Dipterocarpus bourdillonii, belonging to the family Dipterocarpaceae, is listed as Critically Endangered on the IUCN Red List. This tall, canopy-forming tree is a cornerstone of Kerala’s evergreen rainforests, supporting a wide array of flora and fauna. Its dense hardwood has long been prized for construction and furniture, while its oleoresin holds both traditional medicinal and industrial significance. However, decades of deforestation and overexploitation have drastically reduced its population, confining it to small, fragmented patches of forest. The arrival of this new fungal disease adds another serious threat to its survival.

Dipterocarpus bourdillonii

The Pathogen: Corynespora cassiicola

Corynespora cassiicola is a globally distributed phytopathogen that infects over 530 plant species, including crops such as rubber, cotton, soybean, tomato, and cucumber. It thrives in warm, humid climates, conditions ideal in the Western Ghats, and spreads via airborne or waterborne conidia (spores).

In infected plants, the fungus produces target-shaped necrotic spots with yellow halos on leaves, leading to premature leaf fall, reduced photosynthesis, and in severe cases, death of the host. The disease can also cause sunken brown lesions on fruits, which darken and crack over time.

Corynespora cassiicola

First Confirmed Infection in Dipterocarpus bourdillonii

This marks the first recorded instance of C. cassiicola infecting D. bourdillonii. The discovery was made by Dr. Shambhu Kumar, Principal Scientist and Head of the Forest Pathology Department at the Kerala Forest Research Institute (KFRI), Peechi, and Dr. Raghvendra Singh, Senior Assistant Professor at the Department of Botany, Banaras Hindu University. Their findings, published in the June 17th edition of the journal Mycosphere, confirmed the pathogen through morpho-cultural and molecular phylogenetic analyses.

According to Dr. Kumar, molecular identification plays a vital role in differentiating C. cassiicola from visually similar fungal species. This precision allows researchers to design timely disease management strategies and supports broader forest health monitoring efforts.

Fungal infection on critically endangered Dipterocarpus bourdillonii, a tree endemic to the Western Ghats. 

Challenges in Managing the Fungus

Controlling C. cassiicola is difficult due to its genetic diversity and fungicide resistance. Though chemical fungicides such as mancozeb and azoxystrobin may provide partial control, resistance to several fungicide classes, especially quinone outside inhibitors (QoIs) and benzimidazoles, has been documented worldwide.

Therefore, researchers advocate an Integrated Disease Management (IDM) approach, combining cultural and chemical methods:

  • Maintain proper spacing between trees to reduce humidity.

  • Remove and destroy infected leaves and debris.

  • Promote crop rotation and field sanitation.

  • Monitor forest health regularly and avoid human-assisted spread through contaminated tools or footwear.

Beyond Plants: A Broader Threat

Interestingly, C. cassiicola is not limited to plants. It has occasionally been isolated from nematodes and even human skin, where it can cause rare infections like subcutaneous phaeohyphomycosis in immunocompromised individuals. Though such cases are uncommon, they reveal the pathogen’s remarkable adaptability and underline the need for vigilance.

Conservation Implications

The emergence of this deadly fungus highlights an urgent need to strengthen biodiversity conservation in the Western Ghats, a UNESCO World Heritage Site already under immense pressure from deforestation, habitat fragmentation, and climate change. Since much of D. bourdillonii’s remaining habitat lies outside protected zones, conservation efforts must expand beyond forest boundaries.

Collaborative initiatives involving local communities, forest departments, and research institutions are essential to ensure disease surveillance, habitat restoration, and ex-situ conservation measures such as seed banking and controlled propagation.

A Call to Action

This case serves as a stark reminder that plant diseases can accelerate biodiversity loss, especially among species already teetering on the edge of extinction. Protecting keystone and endangered trees like Dipterocarpus bourdillonii is not merely about preserving a species, it is about safeguarding the ecological balance and resilience of India’s rainforest ecosystems.

As the Western Ghats continue to face mounting environmental pressures, science-based conservation and vigilant monitoring of emerging pathogens will be crucial in ensuring that this ancient rainforest, and its irreplaceable species, continue to thrive for generations to come.

Location: India
Welcome to EcoVisionary. I'm Dr. Anitha V, an environmentalist passionate about exploring and sharing insights on the intricate relationship between humans and the natural world. Having successfully completed my Ph.D. in Environmental Sciences, my goal is to raise awareness of pressing environmental issues and inspire actionable solutions for a healthier planet. Through engaging articles, in-depth research, and thought-provoking discussions, I aim to empower readers to embrace sustainable practices and become stewards of the environment. Join me on this journey to create a more sustainable future, where every small step can lead to significant change.

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