Sticky nightshade (Solanum sisymbriifolium), an aggressive and invasive weed, has been officially classified as a ‘regional priority weed’ with an eradication priority across the Riverina Local Land Services (LLS) area. Photo: Landcare.
A new threat is taking root across the Riverina and now also the South West Slopes, causing major concern for farmers and land managers alike.
Sticky nightshade (Solanum sisymbriifolium), an aggressive and invasive weed, has been officially classified as a ‘regional priority weed’ with an eradication priority across the Riverina Local Land Services (LLS) area.
Originally native to South America, the rapid spread of this troublesome plant is posing serious risks to agriculture, livestock and native ecosystems.
First detected in Australia in 1901 near the northern NSW town of Bingara, sticky nightshade has made its way south and east with infestations having been detected in the Riverina and South West Slopes, including the Hilltops, Bland and Cootamundra-Gundagai local government areas.
The plant grows up to 1.5 metres tall and is covered in fine hairs and sharp yellow to red prickles.
It has deeply lobed, sticky leaves measuring five to 14 cm long and four to 10 cm wide, with spines on both the top and bottom surfaces.
During spring and summer, the plant produces star-shaped flowers, which are white or pale bluish-purple with bright yellow anthers in the centre.
Its fruit, small round berries (15 to 20 mm in diameter), turn bright red when ripe and serve as a key method of seed dispersal through wildlife consumption.
According to Riverina LLS, sticky nightshade is more than just an inconvenience.
Multiple, severe frosts can kill the above-ground parts of the plant, but its ability to regrow and flower within just five weeks of germination from underground rhizomes in spring makes it difficult to eliminate entirely.
The weed thrives in diverse environments, including pastures, cultivated fields, waterways, roadsides, and rocky slopes, making its containment increasingly challenging.
Recent flooding has reportedly exacerbated the problem, helping to spread seeds and root fragments from the Central West further west into the Murrumbidgee catchment.
According to Riverina LLS assistant project officer Mel Wilkerson, the weed, previously considered an occasional sighting, had unquestionably become more prevalent since the major flooding of 2022.
“Its spread poses a significant environmental and economic risk, particularly due to its ability to spread quickly via seed and vegetative means,” Mel said.
Sticky nightshade competes aggressively with crops and pastures, reducing agricultural productivity.
Its harsh, sharp prickles make harvesting difficult and discourage livestock from grazing in affected areas.
The plant also produces steroidal glycoalkaloids, toxins that can poison cattle, sheep and other livestock if ingested.
Beyond its economic impact, sticky nightshade poses a physical threat to people, pets, and wildlife as the plant’s pronounced prickles can cause injuries, making manual removal hazardous.
Additionally, its ability to spread through bird and animal seed dispersal, contaminated soil, and cultivation practices means that it can quickly establish itself in new areas if not properly managed.
“If not controlled, it could increasingly severely impact agricultural productivity and biodiversity, as it competes with native vegetation and desirable pasture species,” she said.
Given sticky nightshade’s invasive nature, the Riverina LLS has emphasised the importance of community cooperation in early detection, ongoing surveillance and effective management strategies.
Mel said localised control measures had already proven effective in containing the small infestations.
Chemical treatments, manual removal (with protective gear due to the prickles) of plant and roots and vigilant monitoring are among the strategies being used to combat its spread.
The NSW Department of Primary Industries (DPI) says landowners should avoid slashing sticky nightshade because the berries can grow close to the ground below the slash height.
Farmers should also avoid cultivating infested areas to contain spread of the weed.
Herbicide options are available on the NSW DPI website.
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