The tale of the Jatropha leaf-miner, Stomphastis thraustica in Australia

Abstract

Imported into quarantine from Peru in late 2014 for the biological control of bellyache bush, Jatropha gossypiifolia, the path to the release in Australia of the Jatropha leaf-miner has been thwart with twists and turns. Initially thought to be a new species to science, in 2021 the identity of the insect was determined to be Stomphastis thraustica. Around the same time a leaf-miner found on bellyache bush in Australia was also identified as S. thraustica, though DNA analysis later demonstrated that it is a separate Stomphastis species. Given the time and effort already committed to the project by this point, the decision was made to proceed with the release of S. thraustica. Approval to field release the leaf miner was granted in September 2022. Field releases commenced in October 2022. To date, the leaf miner has been released at 33 sites across Queensland and the Northern Territory. Repeated releases are being made at these sites. The moth is believed to be an adept disperser and once it has established it will readily disperse to other infestations. Stomphastis species cannot be easily differentiated morphologically. The undescribed Stomphastis sp. already present in Australia is widespread, found at nearly all sites where S. thraustica has been released in Queensland, and the Northern Territory. Trials where the two species were forced to interbreed resulted in progeny only when Stomphastis sp. females were crossed with S. thraustica males and these progeny produced offspring. To confirm the establishment of S. thraustica and whether interbreeding occurs between the two species in the field, we will collect larval samples from release sites towards the end of the wet season in 2025 (≥ 2 years after initial releases) for DNA analysis.