Kerala’s rubber plantations face a severe threat from an invasive ambrosia beetle and its fungal partners. Recent research by the Kerala Forest Research Institute has identified the beetle Euplatypus parallelus in alliance with two fungi species, Fusarium ambrosia and Fusarium solani. This beetle-fungus duo causes rapid leaf fall, trunk drying, and reduced latex yield, posing risk to the state’s economy and agriculture.
Identification of the Beetle-Fungus Alliance
The ambrosia beetle Euplatypus parallelus was first noted attacking rubber trees in Kerala’s Irrity-Kannur region. It carries fungi into the tree bark galleries it bores. The fungi farmed by the beetle feed on the wood and provide nutrients to the beetle and its larvae. Fusarium solani’s presence with the beetle is newly reported. Unlike other ambrosia beetles, no fungal storage sacs (mycangia) were found in this species, raising questions about fungal transmission.
Impact on Rubber Trees and Latex Production
The beetle-fungus association weakens tree structure by degrading wood. It causes severe leaf fall and drying of trunks. Infected trees show latex oozing from bark holes. The fungi spread systemically through the xylem vessels, blocking water transport and secreting enzymes that further degrade wood. This results in long-term damage and sometimes tree death, leading to decreased latex output and economic losses.
Biology and Behaviour of Ambrosia Beetles
Ambrosia beetles are native to Central and South America but have become invasive in India since 2012. They attack dead, infected, or stressed trees, often attracted by ethanol released from stressed plants. The beetles do not consume wood directly but farm fungi inside galleries. The fungi break down wood to provide nutrients for beetles and larvae. Their ability to fly allows them to infest many broadleaf tree species.
Challenges in Controlling the Infection
Fungal infections are difficult to control as fungi reside deep inside tree tissues. Insecticides and fungicides often fail to reach systemic infections. Once fungi spread through the plant’s vascular system, recovery is unlikely. Control methods include removing infected parts, burning affected material, using antifungal agents, and trapping beetles. However, these measures require localisation based on plantation geography.
Wider Ecological and Economic Risks
The beetle can infest over 80 species of broadleaf trees including cashew, teak, coconut and coffee. Fusarium fungi are highly virulent and can expand their host range. There is concern about the beetle associating with other pathogenic fungi, increasing damage potential. Fusarium species can infect other organisms and pose health risks to plantation workers, especially those with weak immunity.
Recommendations for Sustainable Management
Experts urge collaboration between policymakers and researchers to devise tailored management strategies. Sustainable treatments like antagonistic fungi and microbial consortia show promise in mitigating fungal infections. Phytosanitary measures successful elsewhere may not apply to Kerala’s unique ecosystem. Focus on localised, ecologically sound interventions is key to managing this threat.
Questions for UPSC:
- Critically analyse the impact of invasive species on India’s agriculture and forestry sectors with suitable examples.
- Comment on the role of mutualistic relationships in the spread of plant pathogens and their implications for ecosystem health.
- Explain the challenges of managing systemic fungal infections in plants and suggest sustainable control methods.
- What are the economic and ecological consequences of plantation crop diseases in India? How can integrated pest and disease management strategies mitigate these effects?
