Options for grass weed control

A new pre-emergence residual herbicide, pyroxasulfone, appeared to give outstanding control of grass weeds, said Syngenta’s head of cereal herbicide research, Matt Cordingley.


The flufenacet-like compound, which has been developed by the Japanese company Kumiai, looks to be very strong in both maize and cereals, giving better control than current standards, Crystal and Liberator, he reported.

But the herbicide’s development track is uncertain, with its first launch being planned for next year in Australia with Bayer, where it will be sold in a mixture with trifluralin.

“It’s nice to know that there’s something new, but it’s not clear yet whether Europe will allow it to be registered at an appropriate rate,” he added. “It has the same mode of action as flufenacet, but it’s more active and more potent. It matches flufenacet at a one quarter rate.”

Whatever the outcome, pyroxasulfone was still a few years away in Europe, he noted.

In the meantime, blackgrass pressure wasn’t going to reduce, so growers must do everything they can to protect the herbicide options they have, said Mr Cordingley.

Resistance to most chemistries, together with the recent loss of herbicides, means that there were few quality options left, he warned.

“There aren’t any novel post-emergence herbicides on the horizon, so Atlantis must be given every chance. That means using pre-emergence herbicides in mixtures and spending as much as you can on that timing, so that Atlantis can cope with what’s left.”

Using the right chemistry at the right time will be important. “Don’t leave it too late. That’s when problems develop and control failures occur.”

Cultural control methods should be used as well, he added. “They can deal with low to moderate populations well. Don’t underestimate the value of delayed drilling, higher seed rates and the plough.”

Mr Cordingley said all agrochemical companies are aware of the commercial blackgrass opportunity. “Selective chemistry has to be better than herbicide-tolerant crops, but there aren’t any post-emergence developments coming along at the moment.

“Atlantis can be protected by the judicious use of residuals. Adding three litres of Defy will boost the control offered by Crystal and Liberator, and it’s also synergistic with Hurricane.”