Act early to combat weeds this spring

Wild oats should be tackled early this spring following limited opportunities to create stale seedbeds or apply autumn herbicides.

With waterlogged fields preventing many farmers from using cultural controls to tackle the weed, some growers can expect to face the challenge of controlling autumn and spring germinating wild oats at the same time.

Poor control means wild oats can outcompete crops for water and nutrients, significantly reducing yield potential, says Kirsty McKenzie, commercial technical manager at crop protection specialists FMC.

“The battle against wild oats isn’t new, but its importance has intensified with changes to autumn herbicide applications and climatic shifts,” she says.

A single wild oat plant per square metre can reduce cereal yields by as much as one tonne per hectare, says Ms McKenzie. “Given their seeds can stay viable for up to 20 years, the necessity for efficient control mechanisms cannot be overstated.”

Understanding the risk factors and employing a comprehensive control strategy is key to manging this persistent weed. “It’s recommended to consult with your agronomist to tailor these cultural controls to your farm.

Alternative chemistry

“Establishing crops with minimum soil disturbance, via direct drilling, can reduce germination of wild oats, and adapting your crop rotation to include non-cereal crops can also help through introducing alternative chemistry.”

But Ms McKenzie says a targeted herbicide application alongside cultural controls can be effective for controlling wild oats. Post-emergence control can be achieved by applying Foxtrot EW  before GS39 in wheat and before GS31 in barley, she adds.

“Wild oat herbicides are most effective and have the best activity against the weed when there are good growing conditions, warmth and moisture. But it is important not to delay applications as larger plants can become more difficult to control.”

Unusual weeds

Alongside wild oats, a number of unusual weeds are also being spotted in winter cereals this spring – prompting questions about whether typical spring herbicide programmes will be effective this spring.

Lack of autumn residual herbicides applied in some areas, easier germination in wetter soils and relatively high soil and air temperatures during the winter months have all encouraged weeds to prosper.

Willowherb, corn spurrey, lesser celandine, and coltsfoot are being reported as out of place this year.

Volunteer beans, although not uncommon, are also causing problems. So are larger than expected populations of groundsel.

Most of these can still be controlled with metsulfuron based products, with more consistent control achieved with metsulfuron and thifensulfuron, or metsulfuron and tribenuron co-formulated products.

Glyphosate ban would mean ‘difficult trade-offs’

A ban on glyphosate would result in wider weed abundance and lower crop yields, suggest scientists.

Although environmental risks associated with the herbicide would be eased, alternative approaches to weed control would have mixed outcomes for the environment, food production and profitability, says the study.

The Rothamsted Research study was led by agricultural ecologist Helen Metcalfe. The findings emphasised the need for careful consideration of the trade-offs if a ban was to be enacted, she said.

Weed communities with evolved resistance to non-glyphosate herbicides were not projected to be disproportionately affected by removing glyphosate – despite the lack of alternative herbicidal control options.

Dr Metcalfe said: “Glyphosate – the most widely used herbicide – is linked with environmental harm and possible human health issues, but it’s use is central to no-till farming approaches.”

The treatment is widely used in arable farming, but in regenerative systems focussed on improving soil health in particular, glyphosate is important for weed control in no-till stubbles and the management of cover crops and leys.

The environmental and health issues associated with glyphosate may trade-off against some of the benefits of moving to more sustainable systems that reduce tillage and integrate cover crops, said Dr Metcalfe.

The study team modelled the impacts of discontinuing glyphosate use and replacing it with alternative control methods for controlling weeds based on winter wheat arable systems typical in northwest Europe.