Growers are being urged not to close the gate on their oilseed rape crops yet, as there is still plenty of time to control black-grass by applying the residual herbicides, Kerb or ASTROKerb. Both products work well in December and right the way through to their cut-off date which is the 31st of January and this year’s conditions mean that the weeds are coming just right for treatment.
“We have seen successful results with Kerb Flo 500 applied in December or January. At this time of the year conditions are generally right to maximise the efficacy of the residual propyzamide, as soil temperatures are below 10°C and falling and the soil moisture deficits are below 50mm and falling. You can check local conditions and spraying advice using the new Dow AgroSciences web-based postcode tool on www.myfarmlifecycle.com or on Farming On-Line,” says David Roberts of Dow AgroSciences.
David says that this year with timely drilling into warm soils, many oilseed rape crops have dense canopies, with few crops being opened up by frost as yet. “Some growers have questioned how this may interfere with the efficacy of Kerb or ASTROKerb. Trials with Kerb Flo 500 have shown that a full oilseed rape crop canopy at time of application makes no difference to final levels of black-grass control.”
Waiting for optimal soil conditions, i.e. soil temperature less than 10°C and soil moisture deficit are below 50mm, to be reached is still the correct approach, he confirms.
“As ASTROKerb is mainly used for black-grass, this should drive application timing. ASTROKerb has both contact and root activity on poppies and mayweeds and in our extensive trials programme, when timed for black-grass control, even when canopies were large, control of these broad-leaved weeds was good. However if, despite our experiences you are still concerned, wait until frost has opened up the crops canopy before you apply these residual herbicides. Kerb Flo 500 may be applied in frosty weather, but do not spray onto frozen ground if rain is forecast as this could result in run-off into watercourses. For ASTROKerb wait until frost is off the weed-leaf and the leaf is dry enough,” David advises.
He points out that this year with high disease pressure in rape, Kerb Flo 500 and ASTROKerb can be mixed with a number of Phoma fungicides including Punch C (flusilazole and MBC), Plover (difenconazole), Proline (prothioconazole) and Sanction (flusilazole).
“The ultimate decision to spray, however, should be based on local conditions, including the ability to travelling and consideration of potential risk to watercourses. Maintaining careful Stewardship of residual herbicides in oilseed rape is vital to ensure the long term availability of these important herbicides,” says David Roberts.
