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Winter weeds to watch out for
The DAFWA biosecurity team would like to remind landholders of their winter weeds and their obligations to control declared/pest weeds.
Officers will be searching transport corridors and high risk areas across the Central Agricultural Region.
It would be of great help if the public could keep an eye out for the following weeds and report suspect plants.
Mexican poppy (Argemone ochroleuca)
Mexican poppy is stiff bluish-green prickly plant that grows up to one metre in height.
It has large, pale yellow flowers, hollow stems and a seed capsule.
However, prior to flowering it resembles a thistle because of its toothed and prickly leaf margins. It reproduces only from seeds which can stay dormant for many years, making control difficult.
In the south west of WA it germinates in autumn and flowers from October to November.
Horehound (Marrubium vulgare)
Erect bushy, aromatic perennial herb, 30-70 cm high, reproducing by seed.
Its leaves are hairy on upper surface and very hairy to woolly on the underside.
Leaves opposite in pairs, rounded up to 7 cm diameter and crinkled in appearance.
The leaf edge is bluntly toothed, veins sunken on upper surface and prominent on lower side.
The flowers are white, 6-10 mm long, formed in dense clusters surrounding the stem at the nodes.
Saffron thistle (Carthamus lanatus)
Saffron thistle is an erect annual thistle to 1 m (rarely to 1.5m) high, a hardy weed of cultivation that displaces more useful species in poor pasture and is arguably the most widespread thistle in Australia.
The spines contaminate wool, and make handling contaminated sheep painful.
It’s seldom eaten, but its seeds are oil and protein rich.
The plant matures with cereal crops and seed is harvested with the grain, and this is one of the main methods of spread.
Wheat contaminated with saffron thistle seed is liable to dockage.
Arum lily (Zantedeschia aethiopica)
Arum lily is a robust, dark green, succulent herb, also known as calla or white arum lily.
It’s found in creeks, irrigation ditches and areas of summer-moist land in the higher rainfall south west of WA, often forming large dense clumps.
Arum lily competes with valuable perennial pasture plants on summer land.
It has been claimed to cause eczema in humans.
Stock deaths have occurred from grazing.
Arum lily spreads vegetatively by regeneration from tuber fragments and by seeds (the seeds can be spread by birds).
Paterson's curse (Echium plantagineum)
Paterson’s curse is an extremely invasive weed that reduces pasture productivity and is widespread in WA.
Paterson’s curse is spread by animals.
The seed has a roughened seed coat that attaches to wool and hair of livestock.
Paterson’s curse is toxic to stock.
Seed can also be transported by vehicles, birds, running water and contaminated hay.
Paterson’s curse seed can lay dormant for years before germinating but is easily controlled in crop as the weed is susceptible to most in-crop herbicides.
Where there are small infestations in pastures, the plants can be grubbed.
There are also several biological controls for Paterson’s curse such as the crown weevil, root weevil, flea beetle and the pollen beetle.
Biological control is not a quick fix, but it can be used against large infestations where eradication is not possible.
If you spot any of these weeds or any plants that look suspicious, please report them to your local DAFWA office or biosecurity officer, who can also provide information on control measures, inspection and herbicide application times.
Now is the time to be searching your paddocks for seed germination of the above plants, please be vigilant on your property.