Sustaining the life of new pre-emergent herbicide Sakura from Bayer CropScience

Australian grain growers will have another tool up their sleeve for grass weed control, with the launch of the new pre-emergent herbicide Sakura® (active ingredient: pyroxasulfone) from Bayer CropScience (AgroNews 2011-11-15).

In a world first, information on the potential for ryegrass to evolve resistance to this promising new herbicide, will be available to growers prior to its commercial release.
Experiments to determine the potential for resistance to evolve to Sakura® were conducted by Australian Herbicide Resistance Initiative (AHRI) researchers Dr Todd Gaines and Dr Roberto Busi in collaboration with Kumiai Chemical Company and the Australian Research Council (ARC).

In a large scale field experiment over 100 million susceptible ryegrass plants were treated with a high rate of Sakura® to determine if there were any major resistance-endowing genes.

"We found the frequency of major resistance-endowing genes in Sakura® was low, which suggests that strongly Sakura®-resistant individuals, in a completely susceptible ryegrass population are rare” Dr Gaines said.

Dr Busi investigated the impact of using low rates, by recurrently selecting a fully herbicide-susceptible and a multi-resistant ryegrass population with sub-optimal rates of Sakura® for three generations.

"We established that the persistent use of Sakura® at sub-optimal rates, can lead to the rapid resistance evolution in a population of annual ryegrass. Sustainable use of Sakura® in rotation with other pre-emergent herbicides is vital to ensure longevity of this important herbicide”, Dr Busi said.

Director of AHRI, Professor Stephen Powles knows too well the consequences of overreliance on herbicides and believes there are some clear messages to learn from this valuable research.

"We know that Sakura is a good herbicide; however like all other herbicides resistance will evolve. It should always be used at the full label rate and in conjunction with an integrated weed management plan, including harvest weed seed management tactics,” Professor Powles said.