Shortages of flufenacet-based chemistry mean growers will have to carefully balance remaining products and take more advantage of cultural controls, advisers say.
Where drilling has been delayed by recent downpours, glyphosate should be used to give grassweeds an early hammering, says Mark Palmer, technical manager for Agrovista.
Some of his growers are managing to apply two glyphosate doses pre-drilling and one with an early pre-emergence spray. “It has made a huge difference on a number of fields, but you need to make sure the crop isn’t coming through.”
The pre-emergence spray should be applied promptly after drilling, particularly if glyphosate is being added, says Mr Palmer. “Pendimethalin mixed with diflufenican or picolinafen would be my preferred option, ideally applied within 48 hours of drilling.”
Growers can then go in with a peri-emergence application of prosulfocarb + clodinafop-propargyl, followed by Atlantis when blackgrass is at the one-leaf stage. Correct application will help improve the activity of these products, he says. “Fine seed-beds and moisture will make a huge difference, but products need to be applied accurately at the right time.”
Dick Neale, technical manager for Hutchinsons, reckons prosulfocarb is the best pre-emergence option for growers who have little or no flufenacet. He recommends 4-5 litres/ha of Defy mixed with 40-60g/ha of diflufenican to be used where blackgrass is less rampant and growers save any flufenacet they have for the worst affected fields “When used at 4-5 litres/ha Defy is at least as affective as Avadex.”
Damp soils will also make the most of the residual products available as they will start working as soon as they contact the soil, he says.
Tri-allate and chlorotoluron (CTU) are also useful actives, but Avadex is difficult to get hold of and CTU is only available in co-formulations. “CTU has to be used pre-emergence to control blackgrass, but when it is it does a good job.”
Growers who need to stretch limited flufenacet stocks should save it for the worst affected fields, lower the rate and mix it with a higher doses of Defy, pendimethalin or diflufenican, says AICC agronomist Steve Cook.
These partners should be selected according to the flufenacet product available. “For example, if you’ve got Liberator, it’s better to opt for Defy or pendimethalin as you don’t need any more diflufenican. If you’ve got Crystal, it’s better to add some diflufenican or Defy.”
Chlorotoluron is a useful active, but because it is only available in a co-formulation with diflufenican, growers need to be careful not to exceed 120g/ha diflufenican, he says. “If you do, you could have problems in following crops, particularly if it’s oilseed rape.”
PRODUCT ACTIVE INGREDIENTS
• Use multiple glyphosate applications where possible
• Use on worst fields and mix with other actives to lower rate
• Pendimethalin and diflufenican pre-emergence followed by prosulfocarb at peri-emergence
• High rate of prosulfocarb and diflufenican at pre-emergence