New research by Rothamsted Research could help growers manage herbicide resistance while protecting existing Avadex chemistry. It follows changes made by the Herbicide Resistance Action Committee (HRAC) – moving Avadex (tri-allate) into the same Group 15 mode of action category as flufenacet, prosulfocarb and ethofumesate. The decision raises questions about whether those products should be used together. Best practice normally recommends mixing or sequencing herbicides with different modes of action.
But Rothamsted scientists say their study has strengthened the case for using tri-allate in grassweed control programmes. The work shows the herbicide acts differently from other Group 15 chemistry.
Fresh evidence
Believing tri-allate behaved differently, plant protection product manufacturer Gowan commissioned Rothamsted Research scientist Dana MacGregor and her team to investigate.
The first experiments compared tri-allate, flufenacet and EPTC, which is not registered in the UK. Scientists studied their effects on blackgrass in controlled conditions. They found tri-allate and EPTC mainly affected shoot growth. Flufenacet affected both roots and shoots.
Further work by Hannah Blyth, Frederick Beaudoin and Alex Borg examined what happened inside the plant. They used biochemical techniques to study changes in plant tissues and cells. The team found tri-allate inhibits fatty acid synthesis, which is essential for plant growth, at two points in the pathway. It acts first in the chloroplast and later in the endoplasmic reticulum. Flufenacet and EPTC affected only the later stage.
“We can say this because when we measure different components within the pathway in our controlled environment experiments, the early ones are altered in response to tri-allate –but not by the other Group 15s we tested,” said Dr MacGregor. The findings suggest tri-allate acts at multiple sites within the pathway. That could explain why resistance has not developed despite more than 60 years of commercial use.
Farm impact
Gowan UK country manager Hank King said the findings had important implications. First, he said, they reinforced Avadex’s role in herbicide programmes.
“Add that to this research, and we have confirmation that Avadex is not only extremely efficacious but is also a proven tool for use as a resistant management partner for existing chemistry.” Additionally, there is no reason to avoid tank mixing or sequencing Avadex with other Group 15 herbicides, said Mr King. The research also comes as many growers rely increasingly on cinmethylin for autumn grassweed control. “Secondly, we see growers in many situations in the UK increasingly relying more heavily on a single active in cinmethylin to do the bulk of the heavy lifting for autumn grass weed control. Where that is the case, we need to be sure the product is robustly protected and supported not only in delivering additional weed control, but also for resistance management. Avadex is a robust partner in this instance as it is delivering a mode of action that acts at multiple sites in the target weed.”
Ongoing research
Mr King said the work also showed the value of investing in science. Better understanding of herbicide chemistry helps growers make informed decisions. It also helps protect the performance of existing products.
“This research is ongoing and will be deepened, which for growers should give them proven and genuine justification for using Avadex to control grass weeds as well as helping protect existing chemistry,” he concluded.