Farmers using residual herbicides to control blackgrass in winter oilseed rape should act now as weather conditions are ideal, say crop experts.
But beware applying chemicals during particularly wet periods, especially before or after heavy rainfall, to reduce any risk of them running into water courses, they warn.
David Ellerton, technical director at distributor ProCam, said now was the best time for farmers to apply propyzamide (eg Kerb Flo) or carbetamide (eg Crawler) to crops.
Soil conditions of around 8-10C are perfect to apply the residual grassweed killers to oilseed rape, he said.
“Applications of residual herbicides should be under way. Usually applications made in November and December offer the best results, but if you want to improve that consistency then add in a contact graminicide, such as Pilot Ultra (quizalofop-p-ethyl).”
Dr Ellerton said there was a wide window for applications of Kerb, which could be made up until the end of January, and the end of February for Crawler – but he said conditions were right now.
However, Dr Ellerton warned of “potentially serious implications” for farmers who may be tempted to “cut corners” and apply the pesticides at wrong times.
“Tactics such as making sure that you leave a big enough buffer zone and avoiding any risk of run-off are key,” said Dr Ellerton.
“But above all, if it is too wet or if there is any risk to water, then just don’t spray and wait until conditions are appropriate.”
The Voluntary Initiative (VI) warned farmers to pay close attention to soil and weather conditions this autumn when applying pesticides.
VI manager Patrick Goldsworthy said: “Paying attention to weather forecasts, soil conditions and drain flow, coupled with the observation of buffer strips or no spray zones alongside any water course should help reduce the risk of pesticides reaching water.”
Dow AgroSciences, makers of Kerb Flo, have produced guidelines to help growers and advisers when applying its herbicide to oilseed rape.
Among the key points it advises are:
• Applications of Kerb Flo should be made when soils are moist, but not waterlogged or saturated, to prevent accidental run-off
• Kerb Flo should be applied when soil temperatures are 10C and falling and weeds are growing slowly
• There is dose rate flexibility, but consider using the full rate of 2.1 litres/ha when tackling high populations of blackgrass
• Mixing or sequencing with contact graminicides such as cycloxydim has shown to further enhance weed control
• Crops must have a minimum of three true leaves before applying Kerb Flo
For more information, call the Dow Technical Hotline on 0800 689 8899.
For the latest agronomy advice from around the country read the Crop Watch blog