Tri-allate offers new hope in herbicide resistance battle

New research suggests that tri-allate could have a valuable role in managing herbicide resistance in grassweeds, due to its multisite mode of action.

This discovery by researchers means the chemical could have a similar role to multisite fungicides in helping reduce resistance for septoria in wheat.

Avadex (tri-allate) is a cornerstone in winter wheat herbicide programmes and it sits within group 15, along with other key actives such as flufenacet.

See also: How cultivation can control resistant Italian ryegrass

Group 15 herbicides are primarily pre-emergence chemicals that stop weed growth by inhibiting very long-chain fatty acid synthesis, restricting cell division in the shoots of young weeds.

However, over the years there have been questions on the grouping label, as little was known about how they worked on blackgrass and the differences between them.

To find out, researchers at Rothamsted research carried out controlled growth experiments and advanced lipid profiling to determine how flufenacet, EPTC, and tri-allate affect blackgrass. They found that they worked in strikingly different ways.

“Looking at physiology or metabolism, it is clear these herbicides don’t all work the same way,” says Dr Dana MacGregor, research scientist at Rothamsted.

“Although these three herbicides are grouped together, their effects on plant growth and metabolism are different.

 “Tri-allate worked in the expected pathway, but it also worked at an earlier point and in a different part of the cell. This suggests there isn’t just one mode of action unlike other members of group 15,” she says. 

There is no evidence of resistance to Group 15 herbicides in blackgrass and not being a single site means it is likely to be robust to resistance developing.

Therefore, as Gowan’s UK and Ireland business manager Hank King points out, experts are beginning to see it as a tool to manage resistance.

“In the UK, we see programmes that rely more heavily on actives like cynmethalin. There is a need to protect these and tri-allate is a robust partner, as it gives mode of action at different sites.

“And also for those concerned about using flufenacet and Avadex in the same programme, they have different modes of action so don’t need to be concerned as they work differently,” he says.