Two diquat alternatives trialled in linseed

Two alternatives to diquat for desiccating linseed crops are currently being trialled, with the aim of being available to growers for harvest 2020.

Linseed growers currently only have two options when it comes to desiccating crops – diquat and glyphosate.

However, the EU ban on diquat will soon leave growers with only one option. Sales of the desiccant will end next month (31 July), with a use-up period ending on 4 February next year.

Therefore, winter linseed being drilled this autumn will be the first crop that growers will harvest without diquat.

See also: Tips on desiccating potato crops without diquat

Nigel Padbury, seeds and marketing manager at Premium Crops, says linseed growers are split down the middle on their preference of desiccant.

He points to the wet harvest of 2017, where they carried out a survey of growers of their harvesting experience that autumn.

“Some 85% said they had a good to excellent experience, while only 5% said they had significant issues,” he says.

Importance of desiccation

It highlights that by sticking to dry days and keeping combine knives sharp, growers don’t have a problem harvesting linseed, he says.

“But this relies on having a good desiccant and the right timing,” Mr Padbury says

The main reason why combining can prove tricky is that linseed is from the flax plant, which is grown for its fibre.

“If you allow fibre to develop, it will start to ret when the stem dries out. The lignin gets harder and all the soft material in the stem disappears.

“Crops that get to this stage can be a nightmare to combine,” he says.

So the key to good harvest ease is to catch the crop early, when the retting just starts, enabling a clean cut. And a desiccant is essential to achieve this, he says.

“The reason some growers like diquat is that, because it is a contact product, you get drying from the top down while the bottom stays green.”

Mr Padbury says this results in a softer stem at the bottom, while the top is dry, with the combine easily cutting through the middle.

Glyphosate option

One option is to switch to glyphosate, but the challenge is that it produces a total-plant effect, as it is systemic.

While the plant does not dry top down, the benefit is that it is a slower process than with diquat. It gives growers more flexibility to time their combining when the stem is still soft.

Some growers prefer this longer window, while others prefer the rapid dry down with diquat.

So with no diquat next summer, Premium Crops has been looking at alternatives, focusing on the potato desiccants carfentrazone and pyraflufen.

“We tried them in trials last year as desiccants and both did exactly the same as diquat. They look promising.”

Replicated trials are being carried out this season, with the two being compared with diquat and glyphosate.

On the back of this, the AHDB has applied for an extension of authorisation for minor use for both products, and Mr Padbury says the hope is to have these extra options in time for summer 2020.

What about pulses?

The Processors and Growers Research Organisation (PGRO) is investigating alternatives, as well as trying to quantifying the need for desiccating peas.