Advice on reducing harvest losses in oilseed rape

Getting pre-harvest management of OSR crops right is essential for minimising harvest losses, which is not just money down the drain, but creates volunteer problems for years to come.

Losses can be high, and while nothing can stop freak hailstorms wreaking havoc with pods close to harvest, Hutchinsons technical manager Dick Neal says there are still ways to mitigate harvest losses. 

“Choosing varieties with in-built shatter resistance is a starting point,” he says. “But also look at varieties with good disease resistance profiles.”

See also: Tips to achieve successful long-term grain storage

He points out that turnip yellows virus, verticillium wilt and light leaf spot can stress the plant or if desiccation is too early, pods can split and open, leading to premature seed losses.

Pests 

Pest infestations such as mealy cabbage aphid, which directly feed on the plant, can remove moisture from it, stressing it and causing pods to split.

“They tend to go for plants already suffering from a disease or areas where, for example, spray treatments have overlapped or there is compaction stress.”

Less use of pyrethroids to treat cabbage stem flea beetle in autumn, due to resistance issues, may be leading to mealy cabbage aphid being more prevalent in summer, Mr Neal says.

“We’re not taking them out like we used to, which isn’t necessarily a bad thing if populations of the early-autumn predator profile that feed on them grow.”

Harvest losses checklist

This harvest

  • Consider a pod sealant
  • Apply pod sealant before desiccation
  • Glyphosate timing also crucial
  • Consider if desiccation is actually needed

Next harvest

  • Variety choice – opt for varieties with pod shatter resistance
  • Also disease resistance can help
  • Consider pest control – mealy bugs can cause pods to split

Pod sealant

Growers should also consider using a pod sealant, he advises.

“Zip-Pod is a polymer that can be applied to the pod, making it more resilient to serious weather conditions such as thunderstorms, hail and high winds.

“It is also a precaution against pods splitting open on the combine table.”

Desiccation can also predispose OSR crops to pod shatter, so growers should consider whether it is necessary, says Mr Neale.

“There is only one choice from a chemical point of view and that is glyphosate. Growers used to grow large areas of OSR and used glyphosate to manage the harvest window. Now areas tend to be lower.”

He believes using glyphosate can only be justified if there is uneven crop ripening.

“Lots of this year’s crops are quite even so will come to harvest at an even rate. There is no reason why we can’t let OSR come to harvest under its own steam.

“If you don’t put glyphosate on, the crop will mature more slowly and losses will be lower, as the pods will be more resilient to shatter.”

It will also save the cost of glyphosate, which is higher this season.

Pod sealant timing

Many growers apply pod sealant at the same time as glyphosate, however, they should be applied separately, says Mr Neale.

“Ideally, you should apply Zip-Pod earlier than glyphosate, when pods are still pliable.”

Even for varieties with pod shatter resistance, it is still worth applying a pod sealant, he says.

“I’ve seen too many crops after a thunderstorm where growers have ended up with a 4t crop on the deck. It is heartbreaking and not worth the risk. It is a belt-and-braces approach.”

There are differences in pod sealants, he says.

“Some are sold as anti-shatter when they are more of an adjuvant. You get what you pay for. They are easier to use these days, but remember to wash out the sprayer as they are a glue.”

Farmer case study: Brett Askew, Gateshead

Growing valuable high erucic acid rape (Hear) on contract, Brett Askew, NFU North East regional crops board member who farms at Grange Farm, Kibblesworth, is keen to minimise crop losses.

He grows 80ha of OSR on his 400ha farm, all of which is Hear variety Ramses. Protecting the crop begins at drilling, where he aims for a seed rate of 30-35 seeds/sq m.

“Using a lower seed rate reduces lodging, which can lead to losses. We also apply a robust plant growth regulator in spring.”

He applies a podstick seven weeks before harvest, which protects the crop from heavy rain, meaning less lodging, he says.

“But it doesn’t protect it against hail and we insure against hail damage – not a lot of people do as it’s quite pricey, but with the value of oilseed rape, it takes the risk out of it being knocked down. In the past we have had to make a claim.”

He desiccates with glyphosate three to four weeks before harvest, saying it is necessary to get a timely harvest in the northern weather conditions he experiences. “If we didn’t, we’d still be harvesting at the end of August.”

Pod shatter resistant OSR varieties

OSR is an expensive crop to grow with high nitrogen, herbicide and fungicide requirements and the worst thing is getting to within a week or two of harvest and experiencing a catastrophic weather event that leads to high crop losses due to pod shatter, says Limagrain arable marketing manager Will Charlton.

“Pod shatter resistance is central to Limagrain’s oilseed rape breeding programme, with all the hybrid varieties it markets from the AHDB Winter Oilseed Rape Recommended List having the trait.

“These are Auckland, Ambassador, Aviron, Aurelia, Antigua, Artemis, Antigua and Clearfield variety Constructor.”

When the company is selecting lines to breed from, pod shatter resistance is a key target, says Mr Charlton.

“The lines we bring forward have that resistance, which was originally bred from a radish. We screen for it at an early stage in the programme and have the markers for it.

“It is a quantitative trait, which basically means if you have it, you have it – it insures against that issue, in this case, pod shatter.”

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