As one of only a small number of products approved for boom application to control fireweed, Trezac builds on its existing use pattern in pastures, where it has already been registered for spot spray application targeting a range of other key weeds.
Trezac Arylex active herbicide has been registered in Australia since 2020 and has been widely used in winter cereals and fallows for the management of some of the hardest‑to‑control broadleaf weeds.
An expanded registration in 2024 allows Trezac to be used in grass pastures via boom application for the control of deadnettle, Mexican poppy and, most importantly, fireweed.
This use pattern gives graziers an effective tool to manage fireweed, which even at light infestation rates is capable of producing more than one million seeds and can rapidly reduce pasture productivity and stocking rates.
Fireweed is not only highly invasive, but also poses a significant risk to livestock health.
The plant contains pyrrolizidine alkaloids, which can cause severe and irreversible liver damage when consumed by animals.
The risk extends beyond grazing, with contaminated hay, silage or grain also capable of poisoning livestock.
Implementing an effective IWM strategy Corteva territory account manager for coastal NSW, Jon Dadd, says reducing livestock health risks while maintaining pasture productivity requires a long‑term, multi‑tactical approach.
“Trezac is an excellent first choice in a fireweed management strategy, to bring plant numbers down in year one of the plan,” Jon says.
“In particular, we see Trezac fitting at the beginning of a pasture rejuvenation program to get a large fireweed population under control without the use of soil disturbance or slashing, which can actually increase fireweed numbers,” he says.
“It’s not an easy weed to manage because seeds are easily dispersed by wind and animals, in stock feed and via mud on vehicles, and its competitiveness means it will easily get a stranglehold on a pasture, and productivity in that paddock will decrease considerably.”
Trezac contains a highly effective combination of Arylex and aminopyralid to control many key broadleaf weeds in pastures.
It also offers flexibility for graziers by enabling robust herbicide mixes to target a broader weed spectrum.
“The product is compatible with other grass and broadleaf herbicides and in many cases, the addition of a mixing partner such as Starane Advanced or MCPA will be required to control the wider weed spectrum,” Jon says.
“Having the ability to alter the rate of the mixing partner will give growers the choice to dial up the control levels to suit their individual needs.”
Getting the best out of Trezac
Trezac is a Group 4 (Auxinic) herbicide, with active ingredients from the pyridine and arylpicolinate sub‑families. These molecules work by disrupting normal growth and development processes within target weeds.
“Trezac’s strong action on legume species means any legumes in the pasture sward will likely be severely impacted following application,” Jon explains.
“We’d suggest graziers set about building their pasture back up by introducing new grass species following the application of Trezac in the first year of the management plan, then spot spraying any fireweed in the second year with Trezac or Grazon Extra.
“Once the fireweed is under control, legumes can be introduced back into the pasture to provide a diverse sward for grazing.”
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