Tropical soda apple (Solanum viarum)

WEED ALERT: STATE PROHIBITED WEED
If you see this plant contact your council weeds officer, the NSW Invasive Plants & Animals Enquiry Line 1800 680 244 or email weeds@dpi.nsw.gov.au

Profile

Impact

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, horticulture and cropping areas. It reduces biodiversity by displacing native plants and disrupting ecological processes. Its foliage is unpalatable to livestock, thus reducing carrying capacities. Prickles on this plant restrict grazing by native animals and livestock and thickets can create a physical barrier for animals preventing access 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.

Distribution

Tropical soda apple is a native of north eastern Argentina, south eastern Brazil, Paraguay and Uruguay. It 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 south eastern states in the USA, where it is now a Federal Noxious Weed. Tropical soda apple has also naturalised in Africa, India, Nepal, West Indies, Honduras and Mexico and outside its native range in South America.

It was first identified in Australia in the upper Macleay Valley in New South Wales (NSW) in August 2010, however it is believed to have been present in this area for a number of years. Subsequent surveys found infestations at Wingham, Grafton, Bellingen, Coffs Harbour, Bonalbo, Casino, Murwillumbah and Wauchope. The smaller infestations have been eradicated and the larger infestations are subject to active control programs. In 2011 infestations were discovered in the Namoi and Border Rivers-Gwydir catchments associated with the movement of cattle from infested coastal areas. Infestations were traced to properties near Tamworth, Attunga and Inverell and are currently the focus of an eradication campaign.

Tropical soda apple has the potential to spread in coastal regions of NSW and Queensland, and inland through cattle movements.

Spread

Tropical soda apple reproduces via seed and can regenerate from root material. In NSW cattle movement is currently the major vector of spread and infestations have been found by tracing cattle movements from infested areas using the National Livestock Identification Scheme. 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 be held in a quarantine area for 6 days before being transported to other properties or to sale. Prevent stock from grazing and moving through infested areas and check cattle handling facilities, cattle camps and yards for seedlings and new infestations.

Description

Tropical soda apple is an upright, 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.

Key identification features

  • 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, 1.5-2 cm wide, with 5 petals. They occur in clusters of 3–6 off a short stem.
  • Mature fruit are yellow and golf ball-size (2–3 cm 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.

Acknowledgements

Authors: Rod Ensbey, John Hosking, Birgitte Verbeek, Tony Cook; Prepared by: Jessica Grantley, Birgitte Verbeek, Elissa van Oosterhout.

References

Plantnet NSW Flora Online;van Driesche R et al. (2002). Biological control of invasive plants in the eastern United States, USDA Forest Service.

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Control

Your local council weeds officer will assist with identification, control information, removal and eradication. Infestations can be spread by inappropriate control activities.

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). Particular care should be taken to remove plants in flood prone areas.

Herbicide options

WARNING - ALWAYS READ THE LABEL
Users of agricultural or veterinary chemical products must always read the label and any permit, before using the product, and strictly comply with the directions on the label and the conditions of any permit. Users are not absolved from compliance with the directions on the label or the conditions of the permit by reason of any statement made or not made in this information. To view permits or product labels go to the Australian Pesticides and Veterinary Medicines Authority website www.apvma.gov.au

See Using herbicides for more information.


PERMIT 9907 Expires 31/03/2020
Glyphosate 360 g/L (Roundup®)
Rate: 200 mL in 10 L of water
Comments: Spot spray application
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate


PERMIT 9907 Expires 31/03/2020
Glyphosate 360 g/L (Roundup®)
Rate: 1 part per 1.5 parts of water
Comments: Cut stump application
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate


PERMIT 12942 Expires 30/06/2017
Glyphosate 360 g/L with Metsulfuron-methyl 600 g/kg (Only products registered for aquatic use)
Rate: 2 L glyphosate plus 10g of metsulfuron in 100 L of water
Comments: Hand gun application, plus wetter
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate


PERMIT 12942 Expires 30/06/2017
Picloram 100 g/L + Triclopyr 300 g/L + Aminopyralid 8 g/L (Grazon Extra®)
Rate: 350 to 500ml in 100 L of water
Comments: Hand gun application, plus wetter
Withholding period: Where product is used to control woody weeds in pastures there is a restriction of 12 weeks for use of treated pastures for making hay and silage; using hay or other plant material for compost, mulch or mushroom substrate; or using animal waste from animals grazing on treated pastures for compost, mulching, or spreading on pasture/crops.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


PERMIT 12942 Expires 30/06/2017
Triclopyr 300 g/L + Picloram 100 g/L with Metsulfuron-methyl 600 g/kg (Various products)
Rate: 350 to 500ml plus 10g metsulfuron in 100 L of water
Comments: Hand gun application, plus wetter
Withholding period: Nil.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


Picloram 44.7 g/kg + Aminopyralid 4.47 g/L (Vigilant II ®)
Rate: Undiluted
Comments: Cut stump application. Apply a 3-5 mm layer of gel for stems less than 20 mm. Apply a 5 mm layer on stems above 20 mm.
Withholding period: Nil.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


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Legal requirements

The content provided here is for information purposes only and is taken from the Noxious Weeds (Weed Control) Order 2014 published in the NSW Government Gazette, detailing weeds declared noxious in New South Wales, Australia, under the Noxious Weeds Act 1993. The Order lists the weed names, the control class and the control requirements for each species declared in a Local Control Authority area.

Area Class Legal requirements
All of NSW 1 State Prohibited Weed
The plant must be eradicated from the land and that land must be kept free of the plant

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Tropical soda apple leafs
Tropical soda apple leafs (Photo: Bec Miller)

Tropical  soda apple leaves are lobed and covered in spines.
Tropical soda apple leaves are lobed and covered in spines. (Photo: Terry Inkson)

Immature fruits are pale green with dark green veins.
Immature fruits are pale green with dark green veins. (Photo: Terry Inkson)

Flowers are white with 5 recurved petals.
Flowers are white with 5 recurved petals. (Photo: Bec Miller)

Leaf spines on a young tropical soda apple plant.
Leaf spines on a young tropical soda apple plant. (Photo: Bec Miller)

A mature fruit, split open to reveal the seeds.
A mature fruit, split open to reveal the seeds. (Photo: Bec Miller)

Tropical soda apple forms dense thickets that impede stock movement.
Tropical soda apple forms dense thickets that impede stock movement. (Photo: Bec Miller)

A tropical soda apple seedling.
A tropical soda apple seedling. (Photo: Bec Miller)

Tropical soda apple
Tropical soda apple (Photo: Bec Miller)

Tropical soda apple fruit
Tropical soda apple fruit (Photo: Bec Miller)

Tropical soda apple plant
Tropical soda apple plant (Photo: Bec Miller)

Tropical soda apple leaf spines
Tropical soda apple leaf spines (Photo: Bec Miller)

Opened tropical soda apple fruit showing seeds
Opened tropical soda apple fruit showing seeds (Photo: Bec Miller)

Tropical soda apple is an upright, branched perennial shrub up to 2 m in height.
Tropical soda apple is an upright, branched perennial shrub up to 2 m in height. (Photo: Greg Egan)