Wet summer could stimulate annual meadow-grass germination flush
After effects of this year’s wet summer could prompt a surge of annual meadow-grass germination in winter cereal crops, says Syngenta field technical manager, Iain Hamilton – particularly in wetter areas noted for the weed, such as Scotland, Northern and Western regions of England, and the South West.
And with only a narrow window for optimum activity from autumn herbicide applications, it will be important to prioritise control between other competing autumn jobs, he adds.
“Annual meadow-grass is a deceptively competitive weed,” says Mr Hamilton. “It doesn’t tower above cereal crops, like wild oats. But it does form a dense, green carpet in the base, choking the crop and draining nutrients.
“After the wet summer, the stage is set for high germination of the weed where soils remain moist. This could coincide with the emergence of winter wheat and winter barley crops. That will offer an opportunity to get on top of it early, but there will only be a limited window to get autumn herbicides applied for optimum control.”
Specifically, Mr Hamilton says the industry is still battling an “IPU mind-set” for annual meadow-grass, whereby IPU herbicide, when it was available, would still control the weed even if fairly well established.
“Since we’ve lost IPU, alternative herbicide chemistry typically used in the autumn needs to be applied early – ideally pre-emergence or early post-emergence of the annual meadow-grass at the latest,” he adds.
“Also, annual meadow-grass tends to emerge with a range of different broad-leaved weed species. Using a tank-mix partner with an annual meadow-grass herbicide allows the spectrum of weeds controlled to be broadened. For instance, a core treatment of 2 l/ha of Defy + diflufenican is a broad-spectrum treatment, particularly for pre-emergence timings. While for early post-emergence timings, Defy + picolinafen/pendimethalin has given good results in recent years.
“An autumn Defy tank-mix can also provide an opportunity to tackle broad-leaved weeds which have developed resistance to sulfonylurea herbicides in places, and take the pressure off a spring sulfonylurea.”
In addition, Mr Hamilton urges growers to take appropriate steps to prioritise autumn weed removal. “This season has seen narrow weather windows for harvesting and cultivations. At busy times, spraying can sometimes slip down the agenda, but recent seasons have shown us that early sprays are critical for good annual meadow-grass control.
“For application, we suggest using the new Defy 3D Nozzles. That is partly for even coverage, since the spray target for early applications is the textured seedbed surface, but also to aid timely spraying, since their drift-reducing properties can mean a greater number of spray days.”