CONDITIONS ARE now much more favourable for applying residual herbicides to control grassweeds in oilseed rape, growers are advised.

“Soil temperatures have dropped and are unlikely to rise again,” said Makhteshim Agan’s Elizabeth Spence. “As a result, residual chemistry applied now will be active through the long winter period, boosting levels of weed control.”

Frosts have also knocked back many forward oilseed rape crops, which means it will be easier to get sprays through the canopy onto the soil, she said.

“It is important to get on when ground conditions allow, perhaps utilising frosts. Where canopy covers are still lush, ensure water volumes are kept high. Any delay from now on will compromise control.”

The best timing for carbetamide products is before Christmas, as efficacy can decline if application is delayed to January or February, she said.

In three years of trials, 85% blackgrass control was achieved from mid-November and December sprays. But where spraying was delayed to January, this fell to 65% and February applications gave 40-50% kill.