Reports of sow-thistles germinating in winter oilseed rape and cleavers not as well controlled as they should be from autumn applications add up to the need for a targeted post-emergence herbicide to tidy crops up and avoid problems at harvest. As well as being visible at flowering, these problem weeds compete directly and smother the crop, making harvesting physically more difficult, and increasing the risk of weed seed contamination and hence admix penalties. Galera (clopyralid and picloram) is the main spring-applied herbicide for winter oilseed rape due to its high level of performance and its weed spectrum which includes cleavers, mayweeds, creeping thistles and sow-thistle.
“The cold weather this year has held back crop development more recently and this means that Galera has a wider spray window than normal. If you have these weeds showing, particularly cleavers, then you really need to get rid of them. The cut-off date for its application is until before flower buds are visible above the crop canopy,” advises David Roberts of Dow AgroSciences.
“Every year in some fields there will be cleavers, sow-thistles, mayweeds and creeping thistles that will need tackling in the spring. Most advisors know from their experience and from farm history which fields these are likely to be. So I would advise that if you haven’t got Galera in store yet, then you need to get sufficient product in to treat these problem weeds in those problem fields. You need to be ready and waiting for both weeds and crops to grow away, when the weather warms up and after nitrogen is applied; this is usually from the end of February, through March and into April,” says David.
“Applied at 0.35 l/ha, Galera will give excellent control of mayweeds, creeping thistles and sow-thistles - and good control of cleavers. To get the best results on cleavers, conditions need to be warm before and after application and the weed less than 150 mm. Groundsel is also well controlled up to the 6 leaf stage. If there are no cleavers, but there are sow-thistles, thistles and mayweed, all of which cause problems at harvest, Dow Shield 400 can be used and will do a great job,” he says.
David explains that Galera has been re-registered recently and so will be available to growers for many more years to come. “For this year existing stocks of Galera, with the MAPP number 11961 and purchased from distributors before the 31st January, can be used throughout 2015 up until the 30th September. In effect it can be used any time now through to April when the crop stage cut-off will come into play. However the re-registered herbicide, which will have a new MAPP number 16413, can only be used from the 1st March and it has no autumn approval. In the future Galera will become a spring-only product, which is when the majority of applications are made anyway.”
“Another label change for the re-registered Galera (MAPP 16413) is that wheat, barley, oats, maize and rape can follow an application within 4 months (or 120 days), but all other crops, such as beans, need to follow an application of Galera after a 36 month period. Once again this shouldn’t affect too many growers, but you will need to keep strict farm records and plan rotations carefully. We are working with CRD in the hope of overcoming this 36 month following crop restriction. As always, growers should check labels before use,” he says.
David Roberts reminds growers to keep pesticides well away from water courses. “Extra care needs to be taken when spraying to avoid any contamination of water courses.”
