NEW South Wales farmers are being urged to check any Paterson’s Curse infestations for insect damage this Spring, before undertaking costly spraying.
Local producers could save money and boost weed control by checking Paterson’s Curse plants for insect damage before they spray weeds, according to the NSW Department of Primary Industries and Local Land Services.
Land managers should look for shot holes in Paterson’s Curse leaves which indicate weevils are on the job. If holes are seen, don’t spray plants now as crown and root weevils can kill the plants, the authorities said.
NSW DPI weed biocontrol scientist, Andrew McConnachie, said buoyant conditions have seen a population boom in biocontrol agents, including crown and root weevils which can kill the weed.
“The weevils are back in force this spring, after drought conditions reduced biocontrol agent populations, and now they have the numbers to make an impact on weeds.
“We suggest producers inspect Paterson’s curse infestations and look for small shot holes in rosette leaves, which are evidence of crown and root weevil damage,” Dr McConnachie said.
“If you find holes in the rosettes, leave the weevils to do the job and don’t spray Paterson’s curse.
“Biocontrol agents will be without a food source and their numbers will drop if weeds are sprayed now,” he said.
Paterson’s Curse reduces pasture productivity and is toxic to livestock. It can also degrade the natural environment, and compromise habitat values by crowding out and suppressing native vegetation. Hay and grain infested with it fetch lower prices.
Dr McConnachie said with the right population levels crown and root weevils can kill Paterson’s Curse plants and its close relative, viper’s bugloss.
“Other biological control agents, a leaf mining moth and a flea beetle, help too by reducing the growth of both weeds.”
Currently six established Paterson’s Curse biocontrol agents are causing significant damage to the weed and biocontrol remains an important component of integrated weed management programs.
Central Tablelands LLS regional weeds coordinator, Marita Sydes, said once their presence is confirmed landholders can take care of biocontrol agents through grazing management and selective spraying.
“The insect biocontrol agents feed above and below ground parts of the plant and are susceptible to harm from grazing animals.
“Paddocks once overflowing with toxic Paterson’s curse are no longer a feature of our landscape,” Ms Sydes said.
“The weed now exists in fragmented, isolated populations, thanks to the biocontrol program.”
The authorities said the Paterson’s Curse national biocontrol program has been an outstanding success, with a net present value of $1.2 billion in 2006, and clearly that figure is substantially higher in 2020.