OILSEED RAPE growers are urged not to overlook the importance of controlling cleavers early-on to reduce combining problems and higher drying or cleaning costs.

While it is now too late for many growers to use more effective pre-emergence herbicides, there are post-emergence treatments available, said independent arable consultant, Steve Harrison.

These later herbicides are Cleaver-suppressors only and tend to give less reliable control compared to pre-em treatments, he said.

“Looking at the Cleaver problem across the arable rotation, it is important not to forget the implications of your actions now on next year’s harvest.”

While quantifying treatment thresholds in oilseed rape is more difficult than for cereals, generally if you have 5-10% cleaver contamination in the crop at harvest, it is equivalent to losing around 15% yield, he said.

“In oilseed rape you can sometimes think you haven’t got a problem, but you never know exactly how big the problem will be until next harvest.

“Oilseed rape was coming in at between 9-12% moisture this year and in some instances needed careful drying. Cleaver seed at harvest is immature with much higher moisture content of around 40% and their presence in admixture will increase drying time and overall costs.”

Where there is still time for early treatment and cleavers are particularly bad, products such as Katamaran or Novall (metazachlor + quinmerac) can offer more flexibility than Centium (clomazone), he suggested.