In News:

Rubber plantations in Kerala, the heart of India’s natural rubber production, are under significant threat due to an invasive insect-fungal association. A mutualistic relationship between the ambrosia beetle (Euplatypus parallelus) and two fungal species (Fusarium ambrosia and Fusarium solani) has caused widespread tree damage, including leaf fall, trunk drying, and reduction in latex yield. This development poses a serious risk to India's rubber economy, biodiversity, and public health.

Key Highlights:

Ambrosia Beetle

• Origin: Native to Central and South America.
• First reported in India: In 2012, from cashew trees in Ponda, Goa.
• Current host: Rubber trees in Kerala, especially in Irrity-Kannur region.

Fungal Partners

• Fusarium ambrosia
• Fusarium solani — first time reported in association with adult ambrosia beetles in India.

Mutualistic Relationship

• The beetles do not feed on wood, but carry fungi into tunnels (galleries) bored into the tree bark.
• The fungi feed on wood, releasing enzymes that degrade plant tissue.
• Beetles and their larvae then feed on the nutrient-rich fungal mycelia.
• This association causes systemic infections in trees, often leading to their death.

Impact on Rubber Trees

• Weakens wood structure
• Causes severe leaf fall and drying of trunks
• Blocks xylem vessels, reducing water transport
• Leads to reduced latex production
• Long recovery time and high tree mortality
• The infection is hard to treat, as fungi lodge deep in plant tissues where fungicides and insecticides are ineffective.

Wider Implications

Scientific Concerns

• Fungi like Fusarium solani can evolve to associate with other beetles, expanding the range of infection to cashew, coconut, coffee, mango, and teak.
• These fungi can spread through soil or be carried by insect vectors, making containment difficult.

Health Hazards

• Fusarium species are opportunistic pathogens in humans.
• Workers in plantations may be exposed to these fungi, especially those with compromised immunity.

India’s Rubber Sector at Risk

• India is the 6th largest producer of rubber globally.
• Kerala accounts for 90% of national production and 72% of cultivation area.
• The economic stakes are high, as the beetle-fungi threat endangers not only latex yields but also the livelihoods of thousands of smallholder farmers.

Response Measures and Strategies

Current Management Practices

• Use of antifungal agents
• Pruning or burning infected parts
• Installation of ambrosia beetle traps
• Chipping infected wood to prevent spread

Challenges

• No mycangia (fungal sacs) found in beetles in India — raises questions on fungal transmission mechanisms.
• Soil- and insect-mediated spread of fungi makes conventional phytosanitary measures ineffective for broadleaf trees like rubber.

Suggested Solutions

• Genetically modified (GM) rubber plants to resist fungal infection (debated).
• Use of antagonistic fungi or microbial consortia inside plants to outcompete pathogens.
• Location-specific strategies based on geography and host tree characteristics.
• Greater collaboration between researchers and policymakers to monitor and contain the threat.