Check oilseed rape for herbicide treatments

Growers have been advised to check their oilseed rape fields now to see what herbicide treatments are needed after the harsh winter.

ProCam‘s David Ellerton says forward planning is essential this spring if rape growers are to maximise the use of the short spray window to control weeds.

The dry autumn meant some growers did not apply pre-emergence herbicides and also reduced the effect of Kerb (propyzamide) and Crawler (carbetamide).

The cold winter spell that followed has potentially left high levels of weeds on rape crops, warns Dr Ellerton.

“We have now run out of time for Kerb and for Crawler. A lot of herbicide was meant to go on, but not all did,” he says.

“So this spring there is probably more weed control to do than for a number of years.”

Large, fleshy climbing weeds such as creeping thistles, sow-thistles and cleavers, should be targeted.

“These weeds are competitive with the crop and cause damage when they interfere at harvest,” says Dr Ellerton.

However, he points out that the choice of spring-applied herbicides in rape is fairly limited.

Dow Shield (clopyralid) can be used to control thistles and mayweeds, while Galera (clopyralid + picloram), which has a broader weed spectrum, controls cleavers, sow thistles and groundsel.

Manufacturers recommend both products are applied when day and night temperatures are above 6C and rising.

But the spraying window for both these herbicides will probably be short this spring, Dr Ellerton warns.

“If you have to wait for the warmer weather and then apply the products within their cut-off, which is up to flower buds visible above the crop canopy, this can be a short time, especially once nitrogen has been applied and crops start to move again.”