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What you need to know about Group A resistance


With wheat and barley in the ground and Wild Oats emerging, now is the time for monitoring crops and making the important post-emergent weed control decisions.

Herbicide resistance is a key driver in the decision-making process and you need to be responsive to the fact that the most common Wild Oat resistance is to the Group A FOP herbicides.

The FOPs are a subgroup within the Group A herbicides and include diclofop (Hoegrass*), fenoxaprop (Wildcat*) and clodinafop (TOPIK®). With widespread FOP resistance, growers are increasingly using herbicides from other chemistries.

According to Syngenta Solutions Development Lead, Ben Parkin, some of those solutions are subgroups within the Group A herbicides, namely the Group A DIMs and the DENs (AXIAL®).

“AXIAL belongs to the DEN subgroup which has a unique chemical structure, its own unique resistance profile, and as such offers the potential to control FOP-resistant Wild Oat populations,” Ben said.

“In most cases AXIAL will be a very effective and robust option for Wild Oat control, even on FOP-resistant weeds.

“Importantly, AXIAL can also have activity on those Wild Oats populations that have developed metabolic resistance mechanism to the DIM subgroup.”

Although not as widespread as Wild Oat resistance to the FOPs, DIM and DEN resistance is developing and Ben recommended “doing your homework”. This may include conducting resistance testing to determine which chemistries within the Group A herbicides offer useful activity to their own populations of Wild Oats.

AXIAL can be sprayed from the two-leaf crop stage up to  first awns visible of the crop (GS12-49) on Wild Oats in a spray topping scenario. Selective Spray Topping (SST) is the relatively late use of a selective herbicide in crop to reduce the amount of viable seed returning to the seed bank.

The registration of AXIAL for SST provides your with a flexible, effective and less environmentally influenced tool to minimise Wild Oat seeds returning to the seed bank.

AXIAL can now be applied in wheat and barley at 200 mL/ha from stem elongation (GS30) to flag leaf sheath opening (GS47) of the Wild Oats plant giving AXIAL one of the widest application windows for Wild Oats control of any product in cereals. This application must be made no later than when the first awns are visible (GS49) of the crop.