Advancing the biocontrol of cat’s claw creeper in Australia: Adding a fungal ally to the arsenal

Abstract

Cat’s claw creeper, Dolichandra unguis-cati (Bignoniaceae), an invasive vine native to South America has been the target of a classical biological control (CBC) programme in Australia (AU) and South Africa (SA) for over two decades. To date only insect agents have been released, with their success often dependent upon local environmental conditions and parasitism. In 2012 a fungal leaf-spot pathogen was observed at field sites in SA causing necrotic lesions and premature leaf drop, often to the detriment of the released insect agents. Identified as Neoramulariopsis unguis-cati and confirmed to be native to South America, its presence likely results from an accidental introduction. Based on its impact and apparent specificity observed in SA and the native range, the fungus was exported to CABI-UK for evaluation as a prospective CBC agent for AU. Specificity testing against 35 species of importance to AU confirmed the high host specificity of the agent, sporulating only on D. unguis-cati. An assessment of infection parameters showed that field infection in AU would likely occur during cooler night temperatures following the formation of dew. The leaf-spot will likely also only infect ground-dwelling forms of the vine in areas with high levels of humidity. An application to release the pathogen in AU was submitted in 2024 and is in the final stages of approval. If successful, the leaf-spot will join the arsenal of CBC agents in the fight against cat’s claw creeper in AU.