Together they’re setting up sites on 10 dairy and red meat farms across the country to demonstrate best practice control and elimination of Californian thistles.
“We know the issue is getting worse; Californian thistles are spreading and the feedback we’ve been getting is that farmers are becoming disillusioned and losing confidence in their ability to stay on top of this problem,” says Corteva marketing manager Glen Surgenor.
“We also realise one of the best ways to promote what can be achieved with a programmed approach control is through using demo sites, and sharing farm case studies.
“But we’re a small team, and we alone don’t have the resources to do this type of extension work at scale, so it made perfect sense to partner with PGG Wrightson on a multi-year national initiative we believe will make a real difference to farmers.”
Corteva technical specialist Nicole Morris is spearheading the company’s involvement, and is excited about the opportunity to combine Corteva’s expertise and product knowledge with PGG Wrightson’s wide outreach.
“This is the first time we’ve done something like this. Their technical field representatives are on the ground across the country, already working with clients who face the challenge of managing Californian thistle, so they’ve been able to help find farmers who want to participate, and we aim to have the programme up and running very shortly.”
By ‘programme’, Morris means a minimum of 18 months’ collaboration between the two companies and demo site farmers.
This will start with an initial application of Tordon PastureBoss this summer at hard-ball stage, followed by MCPA phenoxy herbicide in autumn, and spot spraying of new emerging thistle shoots in summer 2025 with Tordon PastureBoss again.
A critical part of the partnership is a digital portal where farmers can easily record their herbicide applications and access technical information.
Equally importantly, Corteva territory managers and PGG Wrightson TFRs can use the portal to record any observations about key metrics like pasture composition and animal health throughout the programme.
“We want to document and share what happens on these farms as they go through the programme, to show that Californian thistle can be effectively managed with multiple herbicide applications and other tools like mowing,” Morris says.
Tordon PastureBoss is the premium herbicide to use at the front end of a control programme, especially for dense infestations.
The withholding periods are relatively short (three days for milk; seven days for meat) and although it will damage clover, pasture production and grazing is already much reduced where thistle populations are high, and that ground will be re-gained at the completion of the programme, she says.
Now is an ideal time to start a multi-spray programme, because of the plant’s natural growth cycle.
“The reason we recommend spraying in early summer, after flower bud formation but before flowering, is that this hard-ball stage coincides with the time that sugars within the plant are still actively being sent down into the root system, helping deliver the herbicide throughout the plant.
“Once flowering occurs, the movement of sugars stays within the upper part of the plant, for flower and seed development, limiting distribution of herbicide into the root zone, and significantly reducing the effectiveness of the spray application,” Morris explains.
Californian thistle has an aggressive rhizomatous root system, capable of extending more than two metres deep, and adventitious buds produce new aboveground shoots, so the importance of getting chemical to this part of the plant cannot be under-stated, she says.