Two Stomphastis species on bellyache bush in Australia

Abstract

Bellyache bush (BB), Jatropha gossypiifolia has been dispersed worldwide for ornamental and medicinal purposes and has become invasive in many countries. In Australia, BB is a serious weed of northern rangelands and riparian zones and is a target for weed biological control. Exploration in South America identified several potential agents, including a small leaf-mining moth. The leaf-miner was imported into quarantine in Brisbane for host specificity testing and was eventually identified as Stomphastis thraustica. The Peru leaf-miner was approved for release in September 2022, and field releases commenced in October 2022. Releases have been made across Queensland and the Northern Territory. Around the time that the Peru leaf-miner was identified, a gracillariid leaf-miner already known to occur in Australia on BB was also determined to be a Stomphastis species, rather than Epicephala sp. as previously thought. The species has been described as Stomphastis dhileepani. Stomphastis dhileepani appears to be widespread in Australia, having been found at nearly all S. thraustica release sites. Given the prevalence of S. dhileepani, we compared the lifecycle of the two species under glasshouse conditions and conducted cross-mating trials. The results are presented here. Stomphastis species cannot be easily differentiated by external morphology, so DNA analysis is used to confirm the establishment of S. thraustica in the field in Australia and to determine if cross-mating is occurring.