Reports of cleavers coming through early autumn herbicide applications plus the likelihood of thistles and mayweeds too, add up to a 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 harvest physically more difficult, and increasing the risk of weed seed contamination leading to unwanted admix penalties. Galera (clopyralid and picloram) is now the only spring-applied herbicide for winter oilseed rape with a weed spectrum including cleavers, mayweeds, creeping thistles and sow-thistle.

“But Galera has a tricky spray window - from 1^st March up to until before flower buds are visible above the crop canopy, so you need to get ready!” advises David Roberts of Dow AgroSciences. 

“This year that spray window may be shorter than normal as crops are reasonably advanced. But 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 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 must be ready and waiting for both weeds and crops to grow away, when the weather warms up; this is usually from the end of February, through March and into April. The winter has been mild to date, but you never know what February may bring. It could put a brake on rape crops if it turns out cold or it could stay as is and then the crop will continue growing,” 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. The good growing conditions so far for crops have also encouraged weeds growth such as 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.

In order to optimise performance on cleavers, stable air temperatures of at least 6ºC and rising are needed. The warmer and more stable conditions are, the better the results. But it does appear that cleavers are there and will need tackling across the country very soon. You may need to act quickly to purchase the herbicide you require.

Farmers report that they worry about seed return due to cleavers. These weeds are also the most aggressive and competitive of weeds, impacting yield and decreasing percentage oil content. They contaminate seed, increasing the risk of admixture and reducing the price/tonne. “This is just what you do not want at a time when rape pricing is already under pressure,” says Mr Roberts. As well as being visible at harvest, cleavers make harvesting more difficult and costly. Controlling these difficult high biomass weeds will minimise seed return across the crop rotation, helping to reduce the seed burden and herbicide spend in other crops in the rotation.

David explains that Galera was re-registered only last year, overcoming many new and challenging registration hurdles and so will be available to growers for many more years to come.  “The newly registered herbicide, which has the MAPP number 16413, can be used from the 1^st March. So cleavers are out there, go and buy the amount of Galera you will need and be ready and waiting for the opening of the spray window according to the label.”

“Be careful to read the label for the re-registered  Galera, 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 keep farm records and plan rotations carefully. We have commissioned further studies to submit to the regulatory authorities to increase the Galera rotational crop flexibility in the meantime and 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.”