Biological control of Tradescantia fluminensis in Australia and New Zealand
Tradescantia fluminensis (Commelinoideae) is a perennial species native to South America. It is widely utilised as a house and garden plant. It is present in several EPPO countries and invasive in Italy and Portugal. Outside of the EPPO region, T. fluminensis has become a significant invasive alien plant, especially in forest ecosystems in Australia and New Zealand. As part of a classical biological control programme for New Zealand, three chrysomelid insect species (the leaf beetle Neolema ogloblini, the tip beetle Neolema abbreviata, and the stem beetle Lema basicostata) were evaluated and subsequently released in New Zealand. Additionally, a leaf-smut fungus Kordyana brasiliensis was identified from Brazil and following scientific evaluation, it was released in New Zealand. The biological control agents proved effective at supressing T. fluminensis to the extent that in areas invaded, native plants regenerated. Additional research was required to further investigate the host range of K. brasiliensis for Australia, as several species in the family Commelinaceae are native in Australia. In total 28 non-target plant taxa were tested and only the target species developed abundant large lesions. Five taxa developed some small flecks following inoculation with K. brasiliensis though they were resistant to K. brasiliensis. In 2019, initial releases were performed in two regions, the Shoalhaven in New South Wales and Dandenong Ranges in Victoria. Kordyana brasiliensis lesions were detected on T. fluminensis at the 4 plots in the Shoalhaven within a couple of months of the release. In contrast, a few lesions were detected only 5 months after the release at a few of the 9 plots in the Dandenong Ranges. Cooler temperatures in the Dandenong Ranges may have hampered development of the fungus. After 26–32 months, the foliage cover of T. fluminensis had declined substantially in 3 of the 4 plots in the Shoalhaven but had remained stable in the Dandenong Ranges.
Sources
Morin L, Incoll B, Lester J, Zeil-Rolfe I, Gooden B (2022) Biological control of the invasive plant Tradescantia fluminensis with the fungus Kordyana brasiliensis in Australia: Host range and initial releases. Biological Control. https://doi.org/10.1016/j.biocontrol.2022.104978 |