Background

What is the weed problem?

Tropical soda apple is a recently introduced invasive plant in Australia, first recorded along rivers and in paddocks in New South Wales and Queensland in 2010. Due to its ability to form dense thorny stands up to 2 m high, it poses serious threats to livestock management and movement, carrying capacity and native vegetation. The fruit of tropical soda apple are readily consumed by livestock, feral animals and wildlife, enabling the spread and subsequent growth of thousands of seeds per plant. Tropical soda apple is also a secondary host for many diseases and pests of cultivated crops. It has the potential to spread along coastal and riparian regions of NSW and Queensland, and into agricultural areas via cattle, machinery and wildlife movement.

Tropical soda apple fruit containing hundreds of brown seeds (photo: M. Rafter)

How is the weed currently managed?

The whole of NSW a tropical soda apple control zone. Owners and occupiers of land on which there is tropical soda apple must notify the local control authority of new infestations; destroy the plants including the fruit; ensure subsequent generations are destroyed; and ensure the land is kept free of the plant. A person who deals with a carrier of tropical soda apple must ensure the plant (and any seed and propagules) is not moved from the land; and immediately notify the local control authority of the presence of the plant on the land, or on or in a carrier (https://weeds.dpi.nsw.gov.au/Weeds/Details/186).

Tropical soda apple has been the subject of an eradication program led by NSW DPI and Local Control Authorities focusing on containment, eradication and surveillance, including targeted surveillance of high-risk pathways of spread.

In Queensland, tropical soda apple is prohibited invasive plant and the QLD Biosecurity Act 2014 requires that all sightings to be reported to Biosecurity Queensland within 24 hours (13 25 23).

Tropical soda apple is currently managed by manual removal and herbicide treatment, but plants can easily regenerate from leftover roots, and although herbicide kills the adult plant, the seeds inside the fruit remain unaffected.

Cultural management is also important because cattle and horses are attracted to the sweet-smelling fruit which remains viable in the gut for 6 days. Livestock owners need to therefore prevent stock from grazing in infested areas and hold them in a weed-free paddock for 6 days prior to relocation from a contaminated area.

Additional information on current control strategies can be found here:

What can biocontrol offer to the weed’s management?

Evaluating biological control tools during the early stages of invasive weed incursion will enable a back-up management strategy to be rapidly available, should the objective to eradicate tropical soda apple need to change in the longer term.