Published on 16/05/2022
Sharpen was first registered in New Zealand in 2011. Like all Group 14 herbicides, Sharpen is most effective on broadleaf weeds.
But Sharpen has a key advantage over other products with the same mode of action. It has systemic activity within treated plants that can provide effective control of, for instance, atrazine-resistant fathen, through its movement down into the roots.
With the addition of another mode of action into the tank, resistance management can be strengthened. Sharpen is regularly used to expand the activity of other knockdown herbicides such as glyphosate when spraying off pastures. Adding Sharpen to the tank broadens the spectrum of weeds controlled.
It gives excellent knockdown of mallow, fathen, dock, hawks-beard, nightshade, dandelion, willow weed and others. It also speeds up the brown-out of treated pasture.
Of course, glyphosate needs no introduction. It has been the standard knockdown herbicide since it first came to market as Roundup in the 1970s, almost 50 years ago.
It remains the standard today, but there are now more than a dozen different formulations of glyphosate on the market, packaged as over 90 different products.
Herbicides cannot simply be randomly mixed together as some do not make great mixing partners. This may be due to physical mismatches or incompatibility in the way each one works.
Compatibility is not always seen in every instance. The Australian label for Sharpen warns of possible incompatibility with glyphosate, which can reduce control of tropical C4 grasses, e.g., paspalum, but this has not been observed here and hence is not on the New Zealand label.
BASF senior technical services specialist Tim Herman says we cannot really understand why anyone would think there was an issue when the two herbicides have been so widely used in a tank-mix over the last 10 years.
“Apparently there has been a suggestion that adding Sharpen might possibly interfere with glyphosate’s activity against cool season grasses, namely ryegrass. It is always hard to discredit rumours without hard data, so we decided to run trials looking for interference to confirm that there is no such problem.”
BASF tested Sharpen at either 25 g/ha (knock down rate) or 150 g/ha (pre-emergence rate) in mixes with multiple glyphosate formulations (including 360 and 600 gm active ingredient/litre), two adjuvants (esterified canola oil and organo-silicone), with or without acetochlor.
Trials were conducted at three sites across New Zealand. The burndown of pasture (regardless of glyphosate formulation) was not disrupted by the addition of Sharpen and the burn-down of broadleaf weeds was faster.
"Contractors can be confident of mixing Sharpen with any reputable glyphosate formulation for pasture burndown,” Tim says. “Adding Sharpen strengthens resistance management and achieves a better result in a faster timeframe. Given the demands on contractors’ time when there is pressure to burn-off pastures and plant crops, this has to be a win-win for everyone.”
Tim’s only words of caution are that it is essential to read and follow the label instructions for every agrichemical and check the plant-back intervals for every product in any tank-mix.