The ability to cost-effectively mix a selected rate of aminopyralid broadleaf weed herbicide with other cereal post-emergent herbicide partners has put a smile on the face of northern croppers over recent years and it appears it will only widen this year.

The launch of Grindstone by Adama Australia in 2023 introduced a solo formulation of aminopyralid, which previously had only been available in co-formulations with other herbicides.

Jim O’Connor, Adama Australia southern Queensland market development manager, says growers have used Grindstone to create their own post-emergent brews particularly with picloram and MCPA herbicides, and with metsulfuron or fluroxypyr herbicides also added to tank mixes in some cases. 

“It has allowed flexibility with their post-emergent tank mixes, they could avoid using metsulfuron when using the aminopyralid Grindstone, and they could dial the aminopyralid rate up or down to suit their situation,” Jim says.

He says many growers have taken the opportunity to use a higher-than-normal rate of aminopyralid in their tank mixes to improve in-crop weed control and achieve good residual control into fallows and through to the following season.

“They have applied it in mixes at the early tillering stage of crops and looked to suppress weeds through to the next growing season,” Jim says.

“The higher rate of aminopyralid makes the tank mixes better and gives that extra residual punch, resulting in less weeds and cleaner paddocks.

“These mixes have been particularly good against sowthistle and fleabane.”

The ability to select the rate of aminopyralid and other herbicides in tank mixes also allows greater re-cropping flexibility.

Jim says the cost-effectiveness of using Grindstone with a range of tank-mix partners was another major attraction for growers and they also used the mixes to target climbing buckwheat, wireweed and volunteer pulses, as well as prickly lettuce in southern areas.

Grindstone is compatible with a broad range of grass and broadleaf herbicides and doesn’t compromise efficacy of commonly used selective grass herbicides in cereal crops.

Its innovative soluble liquid formulation also is user-friendly and easier to handle than existing granular products. 

“The release of Grindstone has certainly been well received and supported by growers. Its use has exceeded our expectations, and we are prepared for stronger interest in the coming season,” Jim says.

While predominantly used to assist post-emergent and residual control of broadleaf weeds in winter cereals, Grindstone also enhances partner herbicide efficacy of wood weeds including African boxthorn, blackberry, lantana, sweetbriar and wattle in fallows, grass pastures and non-crop situations, as well as cereals.

Jim says, again, the ability to adjust rates of metsulfuron and picloram herbicides with Grindstone was a benefit for these situations, plus using it in tank mixes with herbicides containing triclopyr.

Adam Altmann, an agronomist with Pursehouse Rural at Gunnedah in northern NSW, is very impressed with Grindstone.

It has been included in tank mixes against a range of broadleaf weeds in wheat grown on heavy black soils near Tambar Springs, and while Adam is impressed with its knockdown ability, he also is particularly excited about the residual control it offers for growers.

Grindstone has been mixed with different herbicide partners and compared with other standard broadleaf tank mixes applied at the GS25 crop growth stage, targeting black bindweed, wireweed and some sowthistle and fleabane.

Adam says sowthistle and fleabane were the main broadleaf culprits throughout the region and the additive control provided by tank mixes containing Grindstone was a step up over the other herbicide mixes.

“It has definitely improved the broadleaf control, however the residual control it offers into summer fallows for this region is a big winner and also the reason we are excited about it,” Adam says.

“Due to the amount of cotton grown in the area, in summer we can struggle to use herbicides like 2,4-D. As a result, the aim is to minimise the reliance on knockdown control of these weeds in summer fallows, and Grindstone can help us achieve that.

“Growers can use a higher rate to improve the residual control and still have good plant back ability into a cereal crop sorsorghum.”

He expects popular tank-mix partners with Grindstone could include MCPA as well as Pico ex in-crop and in conjunction with Palmero herbicide for fallow residual.