THE OPEN winter has meant that cleavers have already emerged in oilseed rape crops with added competition from thistles and mayweeds, despite some early autumn herbicide applications and will need a spring clean.

A targeted post-emergence herbicide to tidy crops up and avoid problems at harvest is needed for these problem weeds which compete directly and smother the crop. As well as making harvest more difficult, this increases the risk of weed seed contamination and admix penalties.

Herbicide maker, Dow AgroSciences, said this week that the spray window for the use Galera (clopyralid and picloram) opened on March 1 and it is the only spring-applied herbicide available for winter oilseed rape that has a weed spectrum that includes cleavers, mayweeds, creeping thistles and sow-thistle.

“It can be applied up to just before flower buds are visible above the crop canopy, so you need to get ready. We advise farmers to order sufficient Galera to cover those difficult fields infested with cleavers already,” advised Peter Waite of Dow.

“This year, the spray window may be longer than normal as crops are not so advanced as in the past and most have only just received their fertiliser. Every year some fields will have cleavers, sow-thistles, mayweeds and creeping thistles that need tackling in the spring.

"Most advisors know from their experience and from farm history which fields these are likely to be. You must be ready and waiting for both weeds and crops to grow away, as the weather warms up.”

“Applied at 0.35 l/ha, it 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 in size.”