for more information visit www.dpi.nsw.gov.au/weeds

I&I NSW WEED ALERT SERIES

Weed alert: Tropical soda apple

…have you seen this plant?

Tropical soda apple is an upright much branching perennial

shrub growing up to 2 metres in height. Photo: G. Egan

The large leaves are lobed and the plant is covered in spines. Photo: T. Inkson

Tropical soda apple can form dense thickets which can

impede stock movement. Photo B. Miller

Tropical soda apple, Solanum viarum, is an aggressive prickly perennial shrub 1–2 m high. It invades open to semi shaded areas, including pastures, forests, riparian zones, roadsides, recreational areas, horticultural and cropping areas. It reduces biodiversity in natural areas by displacing native plants and disrupting ecological processes. Its foliage is unpalatable to livestock, thus reducing carrying capacity. Prickles on this plant restrict native animal and stock grazing and can create a physical barrier to animals preventing movement to shade and water.

The plant is a host for many diseases and pests of cultivated crops and it contains solasodine, which is poisonous to humans.

Tropical soda apple was first identified in Australia in the Kempsey area on the Mid North Coast of New South Wales (NSW) in August 2010. However, this weed is believed to have been present in this area for a number of years. The current extent of that infestation is about 50 ha. Subsequent surveys have identified other smaller infestations in surrounding areas, including Wingham and Grafton.

In Australia it has the potential to spread in coastal regions of NSW and Queensland.

World status

Tropical soda apple is a native of north eastern Argentina, south eastern Brazil, Paraguay and Uruguay. In was first recorded in Florida in 1987 and was known to infest 10,000 ha by 1990 and half a million hectares by 1995. By 2007 it had spread to nine other states in south eastern USA. In the USA it is a Federal Noxious Weed aptly named: ‘the plant from hell’. Tropical soda apple has also naturalised in Africa, India, Nepal, West Indies, Honduras and Mexico and outside its native range in South America.

Spread

Tropical soda apple reproduces via seed and can regenerate from root material. In NSW cattle movement is likely to be the major vector of spread. The occurrence of the weed near saleyards in NSW supports this theory. However seed can also be spread by feral animals and birds that feed on the fruit, and via water and contaminated produce, soil and equipment. It is strongly recommended that stock from affected areas are held in a weed free area for 48 hours before being transported to other properties or to sale. Operators of cattle handling facilities are encouraged to be on the lookout for tropical soda apple seedlings at their site.

for more information visit www.dpi.nsw.gov.au/weeds

I&I NSW WEED ALERT SERIES

Tropical soda apple seedling. Photo: B. Miller

Flowers are white, with 5 recurved petals. Photo: B. Miller

Immature fruits are pale green with dark green veins. Photo: T. Inkson

Mature fruit is 20–30 mm in diameter. Photo: B. Miller

Identification

Tropical soda apple is an upright much branching perennial shrub growing to 2 m in height. It has broad based straight cream coloured prickles to 12 mm long scattered on most plant parts.

» Leaves are mostly 10–20 cm long and 6–15 cm wide. The upper and lower leaf surfaces are densely covered in short hairs; mid-veins and primary lateral-veins are cream coloured on both sides of the leaves.

» Flowers are white, with 5 petals 2–4 mm long. They occur in clusters of 3–6 off a short stem.

» Mature fruit are yellow and golf ball size (20–30 mm in diameter). When immature they are pale green with dark green veins, like immature water melons. In the USA plants produce an average of 45,000 seeds.

Control

Individual plants can be manually removed, but care must be taken to remove all the root material, as plants will regrow from root fragments. Fruit should be collected and disposed of appropriately (deep burial or burnt).

The herbicide fluroxypyr (e.g. Starane®) is recommended for control and allowed under the Australian Pesticide and Veterinary Medicines Authority (APVMA) permit PER9907 which expires on the 31 March 2012. Copies of the permit can be viewed or downloaded from the APVMA website www.apvma.gov.au

Prevent stock from grazing and moving through infested areas and manage feral animals where appropriate. Landowners should check cattle camps, yards and feral animal haunts for new infestations. Particular care should be taken to remove plants in flood prone areas.

Combine use of various control tactics detailed above to achieve greatest success for long term control.

Contacts and further information

If you find this weed please help to prevent its further spread by contacting your local Council Weeds Officer or the nearest Industry & Investment NSW office immediately for positive identification and further assistance.

Alternatively call the NSW Weeds Hotline on 1800 680 244 or send an email to weeds@industry.nsw.gov.au

Acknowledgements Authors: Rod Ensbey, John Hosking, Birgitte Verbeek, Tony Cook

Prepared by: Jessica Grantley, Birgitte Verbeek

References Plantnet NSW Flora Online – http://plantnet.rbgsyd.nsw.gov.au/

van Driesche, R. et al. (technical coordinators) (2002). Biological control of invasive plants in the eastern United States. USDA Forest Service FHTET-2002-04.

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