Developing effective management solutions for controlling stinking passionflower (Passiflora foetida) and promoting the recovery of native biodiversity in Northern Australia

Invasive alien plants pose a growing threat to native biodiversity and are a burden to local livelihoods through their impacts on cultural values, agriculture, farming and tourism. A prime example of this is stinking passionflower (Passiflora foetida), a herbaceous vine that has invaded across the global tropics, including vast tracts of remote northern Australia. Yet despite its ubiquity in the landscape and growing concerns about its impacts on native biodiversity, surprisingly little is known about how to effectively control stinking passionflower. To address this knowledge gap, we established an 18 month long field experiment in the semi-arid Pilbara region of Western Australia to (i) understand seasonal variation in the growth phenology of stinking passionflower and identify optimal time windows for management; (ii) compare the effectiveness of different methods for controlling stinking passionflower, including both physical removal and chemical treatments; and (iii) understand the knock-on implications of these treatments for the recruitment of new cohorts of stinking passionflower seedlings and the recovery of native plant species. We found that biomass growth was tightly coupled with rainfall events, which are largely unpredictable in the study region. We also found substantial differences in the effectiveness of the different control treatments we trialled, with glyphosate foliar spray proving highly effective while plants recovered quickly following stem cutting. However, the application of glyphosate foliar spray without the removal of the dead biomass resulted in the rapid regeneration of stinking passionflower seedlings, whereas native plant species largely failed to recover.