Trigger point for broad-leaved weed control in winter oilseed rape
With the mild winter temperatures, many winter oilseed rape crops are forward. Recent wet weather has limited ability to travel and tidy up weeds. This has led to agronomists and growers being concerned about when to treat broad-leaved weeds, cleavers in particular, in oilseed rape this spring.“Galera, based on clopyralid and picloram, is the main spring-applied herbicide for winter oilseed rape as it controls cleavers, mayweeds, sow-thistles and thistles, all weeds that compete with and interfere with the crop. It can be applied from the 4 leaf stage of the crop up to the point just before flower buds are visible above the crop canopy. Usually its cut off is at the end of March or beginning of April. This year with more advanced crops, its cut-off may be a bit earlier, depending on the weather,” says David Roberts of Dow AgroSciences. “In practical terms, the trigger point for Galera applications tends to be when crops and weeds start to grow, usually after fertiliser applications,” he says.He points out that in order to optimise performance, stable air temperatures of at least 6ºC and rising are needed, but preferably 8ºC or higher. “The warmer and more stable conditions are, the better the results. Warm days and cold nights (high diurnal variation) do not suit Galera and weed control, particularly of cleavers, could be reduced. Mayweeds and thistle control is less affected, though.”“Cleavers are the most aggressive and competitive weed, impacting yield and decreasing percentage oil content. They can also contaminate seed, increasing the risk of admixture and reducing the price/tonne. As well as being visible at flowering, these problem weeds make harvesting much more difficult and more costly. Controlling these weeds in oilseed rape will also minimise seed return across the rotation, helping to reduce the weed burden and herbicide spend in following crops – the life cycle approach,” says David.“Applied at 0.35 l/ha, Galera is approved for the control of cleavers, mayweeds, creeping thistles and sow-thistle. To get the best results on cleavers, conditions need to be warm before and after application, weeds should be actively growing and less than 150 mm in size. Groundsel is well controlled up to the 6 leaf stage.”“Farmers plagued with difficult weeds that will impact yield and interfere with harvest will need to have sufficient Galera in their store in readiness for optimum application timings,” he says.David Roberts also reminds growers of their responsibility of keeping pesticides away from water courses. “Extra care needs to be taken at time of spraying to avoid any contamination of water courses. Choosing the right weather and ground conditions and ensuring the sprayer is operated correctly including forward speed and boom height can significantly reduce spray drift.”Galera (267 g/L of clopyralid and 67 g/L of picloram formulated as a suspension concentrate) is recommended post-emergence in all varieties of winter oilseed rape for the control of broad-leaved weeds including cleavers, mayweed, sow-thistles and thistles. It can be applied from the 4 leaf stage of the crop up until before flower buds are visible above the crop canopy. It is recommended at a dose rate of 0.35 l/ha and is compatible with a wide range of graminicides, insecticides and fungicides. It is packed in a 1 litre container.
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