- An invasive eucalyptus weevil, Gonipterus platensis has been identified in the Nilgiri Plateau, marking its first verified presence in the region.
- The initial observation was made via the iNaturalist platform, demonstrating the growing role of citizen participation in biodiversity monitoring.
- Researchers recommend continued surveillance to track its spread and assess potential impacts on eucalyptus plantations and local ecosystems.
A non-native weevil Gonipterus platensis, commonly known as the eucalyptus weevil, has been spotted in the Nilgiris district of Tamil Nadu. The insect was first identified through a citizen science platform, iNaturalist. Its presence marks the first confirmed record of the species in peninsular India and highlights the increasing role of public participation in biodiversity research.
The collection of specimens, including larvae, over multiple years indicates that the population in the Nilgiris is persistent, with the earliest evidence for its presence in the region being March 2019, notes the recent paper on iNaturalist observations.
The initial observation was made by Bengaluru-based Ashwin Vishwanathan, who works for Nature Conservation Foundation, during a visit to Ooty in the Nilgiris. With a habit of documenting biodiversity around him, Vishwanathan uploaded photographs of an unfamiliar beetle to iNaturalist. Based on a suggestion provided by the built-in iNaturalist computer vision model, Vishwanathan identified it as Gonipterus sp. This entry caught the attention of New Zealand entomologist Samuel D. J. Brown, who suspected it might be Gonipterus platensis — a foliage-feeding beetle known to damage eucalyptus trees in several countries.
Brown advised Vishwanathan to consult a local expert, and he contacted Yeshwanth H.M., an entomologist from the University of Agricultural Sciences (UAS) in Bengaluru. A collaborative effort ensued, involving entomologists and molecular biologists, which ultimately confirmed the identity of the beetle.
The researchers recommend further monitoring and assessment of population growth and spread of Gonipterus platensis to minimise the economic impact of this potentially important pest of eucalyptus in India.
Believed to be native to Tasmania but widespread in countries like Australia causing large-scale destruction, this weevil is currently targeting only one species of eucalyptus in the Nilgiris, Eucalyptus globulus, commonly known as southern blue gum or blue gum. “It’s an interesting case of an invasive species attacking another invasive species,” says Vishwanathan.
Invasives and host associations
The paper goes on to describe that several eucalyptus species, native to Australia, Tasmania and nearby islands, have been introduced globally for forestry use. These trees are a key part of the native flora, supporting a diverse array of insect species that have developed close host associations with them. When eucalyptus trees are cultivated in plantations outside Australia, some of these associated insects have also spread, becoming notable pests. Among the most significant of these pests are weevils belonging to the genus Gonipterus (Coleoptera: Curculionidae) such as G. platensis, which has a native range restricted to Tasmania.
G. platensis feeds on the young leaves and shoots, leading to defoliation and potentially affecting tree growth. In regions where it has become invasive, it is considered a significant pest in eucalyptus plantations.
The beetle’s appearance in the montane Nilgiri ecosystem characterised by a diverse range of habitats, from shola forests, grasslands, different forest types as well as plantations, raises questions about how it arrived. The authors of the study suggest that trade in eucalyptus planting material may have facilitated its introduction.
According to ecologist and senior fellow at the Bengaluru-based Ashoka Trust for Research in Ecology and the Environment (ATREE) Priyadarsanan Dharmarajan, the likely pathway for the beetle’s arrival was through imported eucalyptus seedlings or seeds. “The main reason is poor quarantine measures at ports,” he notes. He adds that the increasing movement of goods and people, along with warming temperatures due to climate change, are making it easier for non-native species to establish themselves. He says: “Let’s hope that G. platensis does not become a major pest,” since it is a foliage feeder and not a timber borer.
Introduced during the British colonial period in the 19th century, plantations of eucalyptus trees were established at the Nilgiri Hills of Madras Presidency (now in Tamil Nadu state) by 1843 and later, during 1856. Studies have shown that since the 1960s, eucalyptus species have been grown in large-scale plantations covering over one million hectares across the country and have become a resource of considerable economic value, estimated at over Rs. 480 billion. According to the paper, Eucalyptus grandis is the most widely grown species, but significant plantations of E. globulus, E. citriodora, E. tereticornis, E. camaldulensis, and eucalyptus hybrids also exist. Several pests including Gonipterus weevils have been recognised as threats to the species.
Collaborating with common man
For Vishwanathan, one of the most important aspects of the discovery has been the role of citizen science platforms in biodiversity monitoring. “The greatest takeaway is the significance of citizen science here, as it can help detect and map non-native species, among other things like data collection,” he points out.
Shiny Mariam Rahel, programme coordinator for biodiversity conservation at the Nilgiris-based non-profit Keystone Foundation, who has long used tools like Open Data Kit to track invasive species, also highlights the growing importance of citizen-led documentation. She notes that with climate change, some species previously restricted to specific elevations are now appearing at higher altitudes.
“Some locally distributed invasives are later detected in a different locality, and at different elevations, which is an indicator that certain species are moving upwards due to warming,” she says, adding: “These platforms act as knowledge aggregators and can help scientists gather data for studies.”
While Vishwanathan advocates for more scientists to actively engage with platforms like iNaturalist, Dharmarajan highlights a critical gap in how citizen science is being utilised in India. He believes that the data collected should go beyond documentation and contribute to solution-oriented science. “These data should ideally be used for solution science that benefits citizens,” he says.
The study’s authors note that G. platensis may already be more widespread in southern India than current records suggest. Its ability to disperse, combined with the presence of suitable host trees and the absence of natural predators, makes ongoing observation important.
They recommend setting up monitoring programmes and management strategies to track the spread of the beetle and assess its long-term impact. While there is no immediate cause for alarm, this case serves as a reminder of the ecological complexity introduced species can bring — especially in biodiverse regions such as the Western Ghats. Vishwanathan’s encounter in Ooty demonstrates that everyday observation, when shared and supported by expertise, can contribute meaningfully to our understanding of ecological change.
Read more: A hill town in Nilgiris district pays the price for poor waste management
Banner image: The eucalyptus weevil Gonipterus platensis, photographed in the Nilgiris, is thought to be native to Tasmania. However, it has been found as an invasive in other countries, particularly where Eucalyptus trees are grown. Image by Sankararaman via iNaturalist (CC BY-NC 4.0).
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