16 February 2021, UK: Syngenta grassweed technical manager, Georgina Wood, advocates the earlier treatment reduces the damaging yield effects of competition. It also enables growers and agronomists to tailor rates and application techniques more effectively.
Results of new trials last season showed treatment with Axial Pro at growth stage 25-29 achieved 100% control from rates of 0.5 l/ha, compared to a rate of 0.8 l/ha required to achieve the same results when weeds had increased in size to GS 32-33 and the crop GS 37-39.
She suggests that with a similar pattern of very wet weather through late winter, growers could look to further exploit the trial’s implications this season and counter some of the challenges of wild oat control in the spring.
The two wild oat species affecting UK farms (Avena fatua and Avena sterillis) does mean growers could see protracted germination over the spring.
Identifying and understanding the different populations will help to evaluate the most appropriate control strategies, Miss Wood urged.
“Achieving as high a level of control as possible is essential, since wild oats are more competitive than blackgrass and seeds can remain in the seedbank for longer. Effective control strategies also reduce the risk of herbicide resistance developing,” she advised.
The trials, in Warwickshire, highlighted why the early timing is effective, since both the weeds and crop were at the same growth stage for the initial application. However, by the time of the later application the crop had extended significantly, to four to six stages ahead – and that could impinge on control.
“Early treatment of spring germinating wild oats, whilst the crop is also still relatively open, enables most effective targeting of sprays and facilitates lower application rates to achieve the desired high levels of control.
“Where overwintered wild oats have been identified in the crop, the rates will need to be higher, to control the stronger weeds and their waxy leaf coatings, particularly at the later application timings,” she added.
Research has shown the importance of the highly systemic Axial Pro when weeds are partially shaded, such as by crop leaves, during spraying – achieving faster and more compete control than fenoxaprop-p-ethyl under comparable conditions (below).
It also reinforces the advice to treat when weeds are actively growing to get the best activity, advised Miss Wood.
For herbicide sequencing programmes, Miss Wood points out that where Axial Pro is used first, it can be followed up by a hormone or sulfonylurea treatment after just seven days. However, if the hormone or sulfonylurea treatment is applied first, an interval of 21 days must be left before Axial Pro application.
“With the later application that’s likely to mean the wild oat target would have grown significantly larger, requiring higher application rates for control.”
It is also worth noting that growers can still control weeds such as cleavers, cranesbill and fumitory when they are quite large with follow up herbicide treatments (Pictured above L to R: cleaver; fumitory; nightshade; knotgrass).