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Paddock of purple- Paterson’s Curse spring prevalence

Nov 6, 2020

The Riverina Local Land Services area is seeing a dramatic increase in Paterson’s Curse infestations this spring. There are a few reasons for that. Primarily, we have been coming out of drought that has left plant ground cover depleted and plant competition with weeds reduced. This has provided opportunity for Paterson’s curse to make a come-back and ‘curse’ us yet again.

Many Riverina shires have been affected by Paterson’s Curse this season. Narrandera, Leeton, Coolamon, Junee, Temora, Snowy Valleys, Hilltops, Murrumbidgee, Bland, Lockhart, Hay, Carrathool, Wagga Cootamundra Gundagai and Griffith are all shires that have felt the brunt of Paterson’s Curse this season. Land that has had heavy grazing, land that has been disturbed, along with years of drought and wind impact will often result in the presence of Paterson’s Curse and other weeds.

In previous years there has been great success with biological control agents working on Paterson’s curse. These are insects that consume the Paterson’s curse and have been responsible for successful control over the last decade or so.  Drought has killed off biocontrol across many of the shires, which is disappointing, considering the care that has gone into raising the agents. Many Riverina Biosecurity Weed Officers are re-establishing nursery sites to promote biocontrol agents.

Paterson’s Curse is highly competitive in pastures, outcompeting desirable plants without contributing to forage value. The plant contains pyrrolizidine alkaloids, which are toxic to livestock, particularly horses, though sheep can graze it for a time. Prolonged grazing of Paterson’s Curse is harmful, even to sheep, because the alkaloids eventually cause liver damage, especially if stock consume large amounts of this weed in winter and spring and then graze on common heliotrope over summer.

Impacts from Paterson’s Curse and weeds are the threat to biodiversity. Paterson’s Curse invades native grasslands and woodlands, reducing viable space for desirable species.

All land managers need to be practicing Integrated Pest Management (IPM) practices as opposed to just relying on one method of control, which is mostly chemical. In the 80’s and 90’s land managers relied heavily on chemical application to bring Paterson’s Curse into line.

Recently, the crown weevil and flee beetle have been the most successful biocontrol agents. The NSW Biological Taskforce and Councils across the State have been working consistently, researching and building up biocontrol agent numbers for not only Paterson’s Curse but also other biocontrol for other pest plants. Patience must be exercised for biocontrol agents to build up in numbers to have a significant impact.

Land managers may be tempted use chemical, it is best if they can let the insects re-establish nursery sites to battle the large Paterson’s Curse infestations this year.

Land managers can contact Hilltops Council’s Biosecurity Weed Officers on 1300 445 586 for more information.

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