Uneven flowering within winter oilseed rape crops is complicating the decision over choosing the best timing to desiccate crops this harvest.

Buckinghamshire ProCam agronomist Nick Brown says oilseed rape crops in his region are displaying extremely variable flowering.

“Crops had previously been unable to take up nitrogen and moisture in the drought, but we had a lot of rain in May, which encouraged them to flower again,” he says.

“This secondary flowering is complicating the decision for correct timing of desiccation, because, when you open the pods, the seeds are bright green, whereas the rest of the crop is nearing maturity.”

Crops with uneven flowering are likely to receive a sealant, such as Pod-Stik, to prevent pod shatter and to be desiccated around two weeks later than conventional timing, he believes.

In the east, Essex grower Robert Stevenson is also seeing variability and plans to base his desiccation strategy this year around the field average, but admits: “We could end up with more red seeds if we’re not careful.”

With glyphosate, NIAB TAG agronomist Richard Overthrow says the ideal timing is when around two-thirds of pods in the centre of the plant have turned from green to brown.

“If you go too early, you can kill the plant and stop maturity and end up with a lot of immature red seed and your load could be rejected at the crushing plant.

“However, if you are too late, travelling through the crop can cause considerable damage through seed loss and pod shatter. You might suffer some seed loss, but it is better than having a whole load rejected because of immature seed.”

Glyphosate is the cheapest and most popular form of desiccation, he says. But he reminds growers that it cannot be used on crops that will be sold or saved for seed.

Diquat can be used on seed crops and timing of applications is later than glyphosate, but this method can turn pods brittle and increase shattering, he says.

“It tends to be a bit fiercer than glyphosate and it will desiccate more quickly. The pods become brittle more quickly, which could lead to seed losses if not harvested promptly.”

Swathing is still an option, especially on exposed sites which are prone to wind and variable crops where it is difficult to time a desiccant spray.