A Lethal Partnership: Ambrosia Beetle and Fusarium Fungi

A recent study by the Kerala Forest Research Institute (KFRI) has sounded an alarm over an unusual biological partnership wreaking havoc in Kerala's rubber plantations. The ambrosia beetle (Euplatypus parallelus), native to Central and South America, has been found to carry two fungal species—Fusarium ambrosia and the more concerning Fusarium solani—into the rubber trees' inner bark layers. This is the first known case of F. solani associating with adult ambrosia beetles.

The beetles bore into the trees and cultivate these fungi inside tunnels or “galleries” within the bark. The fungi feed on wood tissue and produce enzymes that weaken the tree structure. In return, the beetles and their larvae consume the fungal mycelia, creating a mutualistic but highly destructive biological loop.

An Alarming Discovery in Kerala’s Rubber Capital

Farmers in Irrity-Kannur were the first to notice abnormal latex oozing and drying trunks, prompting them to alert KFRI via the Tree Health Helpline. Researchers soon confirmed the infestation, revealing how the beetle-fungi duo was silently decimating tree health and significantly reducing latex productivity.

While ambrosia beetles typically infest already weakened or dead trees, they are now being observed attacking stressed but living rubber trees, which may release ethanol—a chemical that attracts beetles. Their lack of mycangia (fungus-carrying sacs) in this case opens up scientific questions about fungal transport and interaction in this specific species.

Impact on Kerala’s Rubber Economy

Kerala accounts for nearly 90% of India’s rubber production and 72% of its total rubber cultivation area. The infestation is not only an ecological crisis but also a major economic threat to millions of rubber farmers. The infection weakens tree structure, reduces latex output, and in some cases causes complete tree death.

Experts warn that controlling such deep-seated fungal infections is extremely challenging. Fusarium fungi reside within the xylem, beyond the reach of most fungicides or insecticides. Once the fungi spread systemically, the tree’s vascular system becomes blocked, leading to irreversible damage.

A Bigger Risk: Future Fungal Partnerships

The most alarming dimension of this threat is the evolutionary potential of these beetles to pair with other fungi. Both Euplatypus parallelus and Fusarium species are invasive and virulent, capable of expanding their host range. With over 80 known host trees, including economically critical species like cashew, coconut, mango, teak, and coffee, the threat may soon outgrow Kerala.

Moreover, Fusarium fungi are opportunistic pathogens in humans and animals, posing a potential public health risk to plantation workers with compromised immunity, as well as to ecosystems at large.

Scientific and Policy Recommendations

The situation demands an urgent multi-pronged strategy. Infected trees must be pruned, chipped, or destroyed, and ambrosia beetle traps should be deployed to limit their spread. However, these are only short-term fixes.

Experts advocate for:

• Location-specific strategies, as Kerala’s unique agro-climatic conditions may not support globally practiced control methods.

• Sustainable biological controls, such as the use of antagonistic fungi or microbial consortia that can resist infection within plant tissue.

• Advanced surveillance and forest hygiene, especially in rubber-growing districts.

• Introduction of genetically modified (GM) rubber plants, which has been proposed by farmers but remains controversial and under regulatory scrutiny.

Given the rapid spread and adaptation of both beetles and fungi, policymakers, agricultural scientists, and local farmers must collaborate immediately to contain the outbreak.