Assessing and managing the threat posed by Epipremnum aureum in South Africa

Abstract

The predictive success of risk assessments is still largely a function of invasiveness elsewhere. Therefore, species that are invasive elsewhere should be prioritised for management, and where possible eradicated. We set out to investigate the threat posed by the alien climber Epipremnum aureum (Araceae) and assess techniques for controlling the spread of the species in South Africa. Epipremnum aureum is highly invasive in Hawaii and Sri Lanka, and has recently been considered as a potential invader in South Africa. However, no study has examined the invasion dynamics of the species. We mapped the species' current distribution in South Africa, modelled its potential distribution globally, and explored control methods. We only recorded the species in the KwaZulu-Natal province of South Africa, comprising 78 naturalized populations and 321 cultivated populations. Delimitation surveys of the naturalized populations revealed ~187,000 plants over ~3 ha. Several of these populations comprised plants as tall as the trees they were growing on, and were often found flourishing in dump sites, along roadsides or as a result of escaping cultivation. Species distribution models showed that E. aureum has a high probability of expanding its current range primarily along the coastal regions of South Africa and into neighbouring countries on Africa's eastern seaboard. Due to the invasion threat of the species, we recommend that all plants outside cultivation be removed. To achieve this, we found that applying herbicides to freshly cut stems significantly reduced plant growth. Given the species' limited dispersal ability and effective chemical control methods, we propose that E. aureum should be listed as category 3 under NEM:BA A&IS regulations, i.e. naturalized populations need to be managed, it cannot be propagated or sold in future, but current garden plantings may remain.