March 26, 2025 | International Journal of Tropical Insect Science |
Researchers from Kerala Agricultural University and ICAR-Central Institute for Cotton Research, India, conducted a study documenting the first confirmed infestation of rambutan (Nephelium lappaceum L.) by the granulate ambrosia beetle (Xylosandrus crassiusculus) in Kerala, India. Rambutan is a commercially valuable exotic fruit crop in the region, and the emergence of new pest threats could significantly affect its cultivation and economic viability.
The study involved field surveys in Kerala, which revealed symptoms consistent with ambrosia beetle infestation, including small entry holes, characteristic "toothpick-like" frass extrusions, wilting, and dieback of branches. The identity of the beetle was confirmed through morphological examination and DNA barcoding, with COX1 gene sequencing showing 99.5% similarity to known X. crassiusculus sequences. Phylogenetic analysis using UPGMA further validated its placement within the species clade.
Additionally, the fungal species Fusarium oxysporum was isolated from beetle galleries, indicating a potential symbiotic relationship that may contribute to tree decline. This association highlights the complexity of the pest threat and its potential impact on plant health.
This is the first report of X. crassiusculus infestation in rambutan in India and underscores the need for targeted monitoring and management strategies to mitigate the risk posed by this invasive pest and its fungal associate.
