Optimising the value of winter oilseed rape in the province

The area of oilseed rape grown across the island of Ireland has increased exponentially over the past number of years.
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For the most part, this has been driven by improved prices. However, the excellent yields achieved by many growers last harvest have added to the impetus behind the crop.

The weather in early September allowed most 2022/23 oilseed rape crops to be planted in good conditions. However, soils were very dry, which compromised the initial establishment in many crops.

But most crops have grown strongly through September and October, in response to the weather.

Rapeseed in Ballykelly, Co LondonderryRapeseed in Ballykelly, Co Londonderry
Rapeseed in Ballykelly, Co Londonderry

However, the wet conditions that so characterised October and November is a worry for many growers, as continuous rain tends to drive foliar disease.

There is now growing anticipation that the upcoming spell of dry weather will improve ground conditions, to the extent that growers can get on with much-needed field work.

Teagasc’s Dr Steven Kildea discussed the disease control options now available to oilseed rape growers on the most recent edition of the Tillage Edge podcast.

He confirmed that many crops are looking well at the present time.

A field of rapeseed at Clough. Co DownA field of rapeseed at Clough. Co Down
A field of rapeseed at Clough. Co Down

According to Kildea, there is a lot of biomass in rape crops at the present time.

He referenced the fact that oilseed planted at Oak Park in Co Carlow have a green Area Index (GIA) of three.

He added: “For the most part, crops went planted out very good conditions. They were then able to hoover-up any nutrients that were available in the soil.

“Some crops might be a little bit behind those established at Oak Park. But, in general, most are looking very well.”

Where disease in oilseed rape is concerned, Kildea indicated that phoma-related problems represent a challenge for many growers at the present time.

“This isn’t that big a surprise, given that conditions were so humid during September,” Kildea further explained.

“A good crop and a strong canopy will encourage the development of phoma. It is a fungus that is directly linked to the development of stem canker.

“The pathogen makes its way into the petiole of the leaf and from there down to the stem. The smaller the plant: the shorter the distance that the pathogen has to travel.

“In cases where there are bigger leaves and bigger canopies, the pathogen has to work that much harder to reach the stem of the plant.”

Another disease that impacts on oilseed rape at this time of the year is light leaf spot. This would be of more concern, from an Irish perspective, as it can cause real damage when buds are emerging in early spring.

Light leaf spot

According to Teagasc plant disease specialist Dr Steven Kildea, not seeing the actual presence of light leaf spot in oilseed rape does not mean that the disease is absent within a specific crop.

He explained: “This is particularly so in crops that have large leaf covers. It’s a case of missing the small lesions.

"However, in smaller crops with smaller leaves, it’s that much easier to pick up on the lesions.”

Kildea discussed the disease threat that can confront rape crops at this time of the year on the most recent issue of the Tillage Edge podcast.

He pointed out that the very wet weather of recent weeks was conducive to the spread of light leaf spot, adding: “We are talking about a wet weather disease.

"Temperatures were quite high over recent weeks, whereas light leaf spot tends to favour cooler conditions, when it comes to its spread throughout a crop.

“Temperatures dropped during the month of November. So this development, in combination with the heavy rain fall, provided the almost perfect conditions for the growth of light leaf spot.”

Recent years have seen the development of oilseed rape varieties with a degree of resistance to light leaf spot.

He commented: “The greater the inherent levels of light leaf spot resistance that we can bring to bear, the more impactful will be the integrated pest control management systems that we can develop.

“Once light leaf spot gets going within a crop, it will produce a lot of inoculum. And even in a resistant variety, come the early spring and if the conditions are right, we could have an epidemic of the disease on our hands.

"This is something that I would be keeping an eye on.”

Kildea also pointed out that light leaf spot is a polycyclic disease. In other words, the fungus creating the disease can complete its entire life cyclea number of times within the same growing season.

“This is why early detection of the problem is so important,” he stressed.

Light leaf spot, if left uncontrolled can reduce rape yields by up to 20%.

Phoma, on the other hand, is not as large a threat under Irish conditions.

But in some cases it can lead to stem canker, early senescence and lodging.

Where light leaf spot control is concerned, the objective is to protect the early flower buds that appear from the middle of February onwards.

Steven Kildea again: “Going in with a fungicide now may only delay the onset of an attack on the flowering buds next spring. But a lot will truly depend on the weather conditions between now and then. Controlling phoma will require the use of the same chemistries: prothioconazole, or proline, for the most part.

“If more than 10% of a rape crop is infected with light leaf spot at this stage, then the disease my need to be knocked back a bit.

“Phoma should be managed now. And the same holds for heavy infections of light leaf spot. But the extent of these diseases will only become apparent when farmers get out and physically walk their crops.”

New varieties

Meanwhile, The Agriculture and Horticulture Development Board (AHDB) has published the online edition of the recommended lists for cereals and oilseeds (RL) 2023/24.

They feature new varieties that deliver large yield increases, especially in barley and oilseed rape. Included are the first new winter malting barley and winter oat varieties to be featured for several years.

Paul Gosling, who manages the RL at AHDB, said: “We've seen relatively few new varieties on the lists this year.

"Several years of plant-breeding advances mean the recommendation bar is set high.

“Relatively few candidate varieties performed better than the best listed varieties to secure a recommendation.”

RL 2023/24 includes several new barley varieties that bring strength to yield and disease resistance.

The winter barley list includes the first malting variety added since 2018. Buccaneer, from Saaten Union, offers a significant yield increase over the established two-row malting varieties, Craft and Electrum, alongside good disease resistance.

Two new two-row and one new six-row hybrid varieties add strength to winter barley feed yields (compared with current favourites). The two rows are Bolivia, from Agrii (bred by Nordic Seed), and LG Caravelle, from Limagrain.

The latter offers a particularly high yield in the East region and a good specific weight. The new six-row hybrid SY Nephin, from Syngenta, is notable for its disease resistance ratings of eight for brown rust and rhynchosporium.

There are six new spring barley varieties under evaluation by the Malting Barley Committee (MBC): three for brewing, two for brewing and malt distilling, and one for malt distilling.

These offer improvements in yield and/or disease resistance (compared with the current market leaders, RGT Planet and Laureate).

The spring barley list also sees the feed variety Hurler added. Bred by Secobra, high yield is its standout feature.

The winter oilseed rape list features three new UK-recommended hybrid varieties: Vegas and Turing, from LSPB, and Attica, from Limagrain.

LG Wagner, from Limagrain, possesses good resistance to light leaf spot.

RL 2023/24 features the first newly added winter oat variety since RL 2018/19. Cromwell, from Senova, offers good yield and grain quality. New spring oat variety RGT Vaughan also features good grain quality.

For winter wheat, the latest RL adds two new feed varieties: the hard-textured Oxford, from DSV, and soft-textured LG Redwald. The latter requires careful lodging management.

In recent years, the RL has seen significant developments in the assessment of disease resistance and lodging traits.

The latest edition features some changes changes, including: young-plant yellow rust resistance in winter wheat; untreated yield data for winter oats and a refined approach to septoria tritici disease ratings in winter wheat.

Review of recommended list selection criteria

AHDB is also confirming that the first phase of a major review of the RL for cereals and oilseeds in the UK is taking place this winter.

Initially, people are being asked to complete a questionnaire as part of efforts to improve the variety trialling project.

The announcement follows a strong endorsement of the RL by Agriculture and Horticulture Development Board (AHDB) levy payers earlier this year, where the project scored 4.2 out of 5.0 for importance during the “shape the future” process.

Courtesy of this initiative, participants were asked to rank AHDB work priorities in terms of importance to the cereals and oilseeds sector (from 1 to 5, where 1 is low and 5 is high).

Subsequently, the AHDB Cereals & Oilseeds sector council pledged to conduct a major review of the RL in its five-year sector plan.

Jenna Watts, AHDB head of crop health and integrated pest management, said: “We need to hear from farmers to help us hone the RL so it continues to fit the complex decision-making needs of modern farming businesses.

“This is a thorough review and will leave no stone unturned. It will cover many aspects, from the type and nature of the trials to the way data is analysed and variety decisions are made.

"It will also investigate how results reach farmers and ensure that the RL continues to deliver the best value to industry.”

Typically, the main RL project runs in five-year phases, with a large-scale public review conducted during each project phase to inform subsequent activity.

During the previous project phase (2016–21), AHDB conducted the 'Look Ahead' review.

This highlighted the importance of the whole variety package rather than the more traditional focus on yields.

In response, the RL changed the way it assessed many traits, including disease resistance and lodging traits.

It also led to the development of enhanced digital formats, providing powerful ways to view RL data, such as through the RL app and variety selection tools.

The questionnaire, which can be accessed on the AHDB website, focuses on levy payer requirements.

"However, in-depth discussions will also take place at stakeholder meetings and focus groups over the winter to capture the wider requirements of the industry.

"A dedicated review steering committee has been established to lead the project and provide recommendations to AHDB on potential improvements to the RL.”

Patrick Stephenson, independent crop consultant, AHDB Cereals & Oilseeds sector council member and chair of the RL wheat crop committee, has been appointed to lead the review steering committee.

He explained: “This review looks forward and aims to keep the RL robust in the face of numerous challenges facing the industry.

“With constraints on budgets and small-plot trials, it is not possible to do everything.

"However, the review will help us focus activity. I am particularly keen to squeeze every ounce of value out of data to make the RL even more relevant to farmers.”

The questionnaire is open until 17 February 2023, with initial results due to be published next spring.

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