With cereal volunteers and grassweeds growing fast in oilseed rape crops, it is worth picking the most appropriate herbicide treatments, say agronomists.

Most volunteers have emerged by now, says Frontier’s Bob Mills.

Indeed many growers have already applied the first of split doses of cheaper graminicides (see table) to remove first flushes of competing barley or wheat, he notes.

There is plenty of choice of post-emergence products, but where blackgrass is an important target the slightly more expensive of the contact-acting products – eg, Aramo and Laser – should be considered, advises Mr Mills.

There are suggestions that cycloxidim is less effective on wheat volunteers than other options.

But at the dose required for blackgrass there should be few escapees, TAG’s David Parish believes.

Given widespread good growing conditions many crops are already large enough to accept residual-acting post-em products, but growers should wait for cooler conditions, warns Mr Mills.

Carbetamide is slightly cheaper than propyzamide and being more mobile in the soil is best suited to crops established after ploughing, he suggests.

“Kerb is especially useful on min-tilled and Autocast crops.”

Both need moist soils to work well.

The general perception is that Kerb should be applied late, says Mr Mills.

“But the earlier you get on, when the blackgrass is small, the better the control.”

andrew.blake@rbi.co.uk