Stevia ovata – not so sweet

Abstract

Native to elevated areas of the tropical Americas, Stevia ovata Willd (candyleaf) does not have a record of weediness overseas. Closely related to Stevia rebaudiana Bertoni (a commercially grown sweetening agent), S. ovata, with its pretty white flowers and soft sweet-scented leaves, may not seem like much of a threat. However, affected land managers in north Queensland’s Atherton Tablelands know better. The woody multi-stemmed perennial shrub has infiltrated open habitats, including cattle grazing lands, and road and power line corridors. Its rate of spread and formation of virtual monocultures is a growing cause for concern. S. ovata’s observed weedy behaviour in these situations, coupled with the fact that this region has the only known infestations in Australia, has led to its local declaration by the Tablelands Regional Council, and the formation of the S. ovata Working Group. Keen to quash further S. ovata infestation, this group of concerned stakeholders initially requested research into the ecology and control of the plant, and were a driving force behind a successful multi-agency delimitation exercise which took place in June 2015. Biosecurity Queensland took up the research challenge and investigated several aspects, including seed longevity, seed dispersal, growth rates, reproductive age and size, lifecycle trends and control options. This paper presents an overview of S. ovata and its history of in Australia, and describes our research into its ecology and control.into its ecology and control.