15 Oct 2019
Weeds are now tougher and harder to kill than ever, thanks to their increased resistance to herbicides, according to a leading agronomist.
New approaches are needed that tackle them without these chemicals, such as precision weed monitoring, electric and foam weed control, Dr Nicola Cannon of the Royal Agricultural University (RAU) said.
Speaking ahead of the Changing Face of Weed Control conference at the RAU this month, Dr Cannon, Associate Professor of Agriculture, explained: “Weeds have been one of the main challenges to farmers and gardeners ever since humans started cultivating the land. They compete with our crops for light, water and nutrients and so reduce yields.
“Historically weeds have been controlled by manual removal, sheep grazing and diverse crop rotations which helped deprive them of a rich environment for growth.
“The Second World War saw the breakthrough discovery of 2, 4-D, a selective herbicide that could kill broadleaved plants but left the growing cereal or grass crop undamaged. This product is still widely used in agriculture today and further herbicide groups have been discovered, many of which act by mimicking plant hormones and interfering with the growth of the target weed to be killed.
“Herbicides have become a mainstay of conventional farmers’ weed control strategy, but for a couple of decades now the cracks have started to show in this method of weed control as they have become ever more resistant to the herbicides applied.
“Initially the weeds are only weakened and not killed and then in many cases previously susceptible weeds are able to continue germinating, grow and seed, thereby increasing the resistant weed populations. 
“New herbicides are now very rare to come to market because finding suitable active ingredients which work effectively and pass the stringent pesticide registration process is very demanding, expensive and takes many years of product development.
“So, weed resistance, coupled with the lack of new products, have left farmers facing huge challenges in weed control. Previously available herbicides are being withdrawn due to either environmental or human health concerns.
“Growing crops with fewer or no herbicides requires different approaches, some traditional but also the adoption of innovative techniques, such as weed mapping and control solutions by techniques such as robot or drone spot spraying or physical removal.”
The Changing Face of Weed Control is a farmer focussed event - featuring speakers from the RAU, ADAS and the Soil Association - that looks at the application of these new techniques.
Held at the University’s Rural Innovation Centre (RIC) in Cirencester on 23 October, it will feature field demonstrations including new prototype weed control solutions, machinery options and environmental management.