Tracking weeds using NLIS – tropical soda apple
By Rachel Gordon, Livestock Biosecurity Network Biosecurity & Extension Manager
We usually think of the National Livestock Identification Scheme (NLIS) as a method of identifying cattle, sheep and goats. Specifically, where they’ve come from, and where they went to. It is used to trace stock in disease outbreaks, food contamination issues, and return lost or stolen livestock. It can also be used to locate exotic plant infestations.
Tropical soda apple (TSA) (Solanum viarum) is a noxious weed that originates from South America but had spread to areas of North America, Africa, India, Nepal and parts of Asia. It was first identified in Australia on the Mid North Coast of New South Wales, near Kempsey, in 2010. It is a perennial shrub that grows to approximately one to two metres high. It has large, unpalatable leaves, is covered with spines and produces mature, yellow fruit the size of golf balls. In the immature stage, the fruit resembles small watermelons, pale green with dark green veins. The plant can produce up to 200 fruit, each containing up to 200-400 seeds. A single plant can produce up to 45,000 seeds each year.
TSA is a problem for several reasons: it spreads quickly, invading areas along river banks and pastures. It also establishes in forests, along roadsides, and in horticultural and cropping areas. Because of its prickly nature, TSA can prevent animals from reaching water and shade. Its family members include eggplant, potato, and tomato, and it can carry plant pathogens such as cucumber mosaic virus and tomato mosaic virus posing a risk to our horticultural industry.
Cattle can play a significant part in spreading TSA. While the plant itself is not palatable, the fruit is attractive to cattle. The viable seeds are spread through manure up to six days from ingestion. Any seed not passed within six days becomes unviable. Tracing cattle movements through the NLIS has been successful in locating TSA infestations.
Simple biosecurity measures can reduce the spread of TSA. If you are buying cattle from areas where TSA may be an issue, such as the North Coast of NSW, you must hold any incoming cattle for a minimum of six days in an area that can be closely monitored for seedlings.
Similarly, if you are selling cattle and they have had access to TSA, you must hold them in a clean paddock for a minimum of six days prior to moving them off your property. It is illegal to move cattle, knowing they may be carrying TSA seeds. These movements are traceable, and you can be prosecuted and fined for transporting TSA seeds via cattle movements.
Seedlings have also been known to germinate in horse manure, so incoming horses should be held in a contained area for six days as well. Other forms of movement include waterways, feral animals, birds, and contaminated fodder, soil, and equipment.
If you are in a TSA area, or suspect you might have bought livestock from a TSA area, take the time to check for new plants. Regularly monitor cattle camps, stockyards, areas where cattle have been fed, and holding paddocks. Monitor waterways such as drains, gullies, and floodplains. Check fence lines, tracks, roads, forested areas and places where feral animals inhabit.
If you find, or suspect TSA, contact your local council weeds officer as soon as possible. TSA can produce fruit within two months of germinating, and while herbicide will kill the plants, it will not kill the seeds within the fruit.
To bolster biosecurity on your farm, download the free FarmBiosecurity app.
- Rachel Gordon is one of LBN’s Biosecurity & Extension Manager. She can be contacted on 0488 400 207 or email firstname.lastname@example.org.