Sodden soils have severely hampered early weed control opportunities this season, and a wet and mild winter, which is typically followed by higher spring grass-weed populations, could make the challenge even greater.
The more prevalent common or spring wild oat typically hits peak germination in March and through April, which could prove especially competitive with the increased areas of spring cropping this season.
Meanwhile, winter wild oats typically geminate around October and where there has been no opportunity for pre-emergence herbicides in winter crops, they will have escaped control.
Alongside a lack of herbicide opportunity, the absence of harsh winter conditions this year may also result in increased survival of weeds, says Syngenta technical manager, Georgina Wood.
“Any conditions which limit weed growth in the spring can be challenging for effective control. The cool, dry conditions experienced in the past two seasons have been particularly difficult for post emergence grass-weed control,” says Miss Wood. “Herbicides need active growth to be effective.
“Movement of pinoxaden through wild oats is faster than fenoxaprop, resulting in faster kill, especially in more challenging conditions,” she claims.
According to Syngenta, in cold conditions with frost on 50 per cent of nights, pinoxaden gave better control of wild oats and rye-grass, compared to clodinafop, even when growth was limited.
“Herbicide translocation within the target weed is crucial when some tillers may be shaded from application,” Miss Wood adds.
That makes application techniques in the spring especially important to get good coverage of the target weeds.
To achieve good coverage, Miss Wood advises using an angled 3D Nozzle whilst the crop and weed are still small, but switching to a 90 per cent drift reduction or Amistar Nozzle when crops are larger and weeds more shaded by the canopy.
Agronomists should also be aware of herbicide sequencing rules when timing pinoxaden recommendations.
“Where an SU/hormone herbicide has been applied first, growers must wait 21 days before applying Axial Pro, but where the Axial Pro is applied first an SU/hormone herbicide can be used after seven days later.
“That decision, assessing levels of wild oat emergence and weed sizes, may influence timing and rates to achieve the best overall control,” she adds.
Although some germinate in autumn, tiller in early spring and are resistant to frost, most germinate in the spring. One wild oat plant/sq.m can reduce yields by up to 1 tonne/hectare in winter cereals and up to 0.6t/ha in spring cereals.
Cultural controls for wild oats include: