Significant numbers of UK arable farmers are using glyphosate to tackle grassland weeds up to six times in a single season, according to Dr Paul Gosling, a herbicide specialist with the Agricultural and Horticultural Development Board (AHDB).
“Black grass is a particular problem on many farms, particularly in the East of England,” he said.
“And the application of glyphosate, pre-drilling, is the only way of controlling the problem at the present time.
“But there are a number of gaps in our knowledge regarding the most effective way of using glyphosate in this context.
“We are aware of glyphosate resistance becoming an issue within perennial ryegrass populations on the continent. And the last thing we want is for the same problem to arise amongst grassland weeds here in the UK.”
Gosling confirmed that a £500,000 programme of research work is set to investigate potentially ‘high-risk’ farming practices to help minimise the risk of glyphosate resistance developing in UK grassweeds.
“The work will be carried out by the Agricultural Development and Advisory Board over a five-year period,” he said.
“It will look at two key risk glyphosate periods: the use of the herbicide on stubbles pre drilling and its application between crop rows, where larger weeds are concerned.
“The work will entail a mix of full blown field trials and potted experiments. Four distributor companies will also contribute to the work through the provision of data and trial sites.”
Gosling believes there is no risk of glyphosate being banned as a herbicide in the EU.
However, he drew a difference between the use of the chemical as a broad spectrum weed killer and its application as a pre harvest crop desiccant.
“These are two entirely different scenarios,” he said.
“I am fully aware of the fact that glyphosate residues have been found in bread samples. But this has no bearing, whatsoever, on the use of the chemical as a herbicide.”
Blackgrass (Alopecurus myosuroides) is an annual weed that can reach heights of 80-90cm.
The stems are round and slender with few nodes. The leaves are hairless with no auricles and the ligule is long, blunt and finely serrated.
The flowering head is a compact spike 3-6cm long, narrow and pointed, often with a purple tinge. Spikelets are single flowered with prominent awns.
Blackgrass is a major problem to UK farmers. As an individual plant it is not as competitive as wild oats, but because populations of 200-400 plants per square metre are quite common, yield penalties are severe.
It has been calculated that just 12 plants/m2 can reduce yield by 5%.
Seed is shed before harvest thereby replenishing the soil seedbed.