OSR disease resistance a vital part of variety choice

The new oilseed rape Recommended List reflects a changing landscape, with increased focus on varietal resistance for reliable yields.

Both lists are seeing newcomers offering 7s and even 8s for the two biggest disease threats to rapeseed yields, while one candidate has a 9 for phoma.

North list newcomer Nikita brings a 7 for light leaf spot, while Barbados boasts a 7 for both phoma and light leaf spot.

Alizze makes it on to both the East/West and North lists, with a 7 for light leaf spot, and Angus makes a debut on the East/West list with a phoma resistance score of 8.

See also: How the new oilseed rape varieties affect farmers

Sarah Middleton, Bayer’s seed product manager, says disease resistance is now firmly at the forefront of oilseed rape production.

“It is clear the Recommended Lists are shifting towards better phoma and light leaf spot resistance.

“The RL committee has moved the minimum requirement for both diseases up to a 5 and there is talk of that going up to a 6 in the future. I think there is only going to be more of a drive for greater varietal disease resistance in years to come.”

With a 9 for phoma and 7 for light leaf spot resistance, candidate variety InVigor 1030 is evidence of this, adds Ms Middleton.

The candidate variety, which is up for recommendation for the 2017-18 list, is being trialled this season on five farms across the UK.

The role of resistance

One of the trial farmers is Cambridgeshire Fenland grower Rex Heading, who is growing InVigor 1030 under farm conditions, alongside 26ha of mostly Harper and a smaller area of Elgar.

He sees improved varietal resistance as a crucial part of growing the crop on his 162ha farm.

“As we lose more of the chemicals we need to control disease, resistance will become more important.

“Yield and resistance are now equal factors when choosing our rapeseed varieties. Standing ability is important too, because it is better for combining.”

Phoma is now the second most important disease in oilseed rape, after being overtaken by light leaf spot in the past two years.

Bayer commercial technical manager Darren Adkins lists spray timing flexibility as one key advantage of growing a variety with greater disease resistance.

“Fungicide costs haven’t changed much, but you can afford to spray later now than you would have done historically because of this improved resistance.

“You would be particularly worried about getting your fungicide timing right on varieties with a score of less than 6 for phoma,” he says.

Phoma spores on oilseed rape

Early phoma in oilseed rape.

Early phoma in oilseed rape.

Mr Heading says phoma has always posed the biggest risk to his crop, but he explains that in recent years light leaf spot, traditionally perceived as a disease of the North, is becoming more of a problem.

However, he says his crops haven’t suffered too badly with light leaf spot in the past couple of years, putting this mainly down to the 6 rating for his crop of Harper.

But such is the pressure of disease in his part of the country, about 10 miles east of Peterborough, he feels there is little scope for cutting fungicide applications as varietal resistance improves.

“The idea that you can save on your fungicide applications is lovely, but I think you still want to have a full package [fungicide + resistance] to fight disease.”

Instead, he sees resistance being valuable in seasons when there are few opportunities to spray due to wet and windy conditions, as it does offer some protection.

Scottish perspective

There has traditionally been a much greater focus on disease resistance in Scotland, because of the higher pressure. Therefore varieties offering 8s and 9s will be particularly welcomed by Scottish growers.

Scottish disease expert Fiona Burnett says light leaf spot continues to be the dominant disease north of the border, but adds that phoma is being seen more in crops nearer the Scottish border.

“We are seeing more of it, but it still isn’t as damaging to yields as it tends to be in England, or when compared with light leaf spot.”

She notes AHDB data shows there is a good correlation between disease resistance and reliable yields.

She says Scottish oilseed rape growers should opt for varieties with stronger LLS resistance, such as Barbados, Nikita and Alizze, as this will offer more reliable yields than chasing for that extra 1-2% gross output.

“If you get a new variety come along that offers a 2% increase in yield, but isn’t as strong on LLS resistance, that extra output can easily be wiped out by the 15% reduction in yield that a moderate LLS infection can bring,” she argues.

When it comes to the role that strong varietal resistance can play in helping with fungicide costs, Prof Burnett talks of a “sliding scale”.

“You should try to tailor your fungicide plan to the disease resistance of the crop. It depends the season, but if you have an 8 or a 9 for LLS, you may be able to cut your fungicide application back.”

Location does have a bearing on this theory, however, with crops grown in high-risk LLS areas, such as Aberdeenshire, more likely to need a full fungicide package paired with highly resistant varieties, she adds.

The new oilseed rape Recommended List reflects a changing landscape, with increased focus on varietal resistance for reliable yields.

Both lists are seeing newcomers offering 7s and even 8s for the two biggest disease threats to rapeseed yields, while one candidate has a 9 for phoma.

North list newcomer Nikita brings a 7 for light leaf spot, while Barbados boasts a 7 for both phoma and light leaf spot. Alizze makes it on to both the East/West and North lists, with a 7 for light leaf spot, and Angus makes a debut on the East/West list with a phoma resistance score of 8.

Sarah Middleton, Bayer’s seed product manager, says disease resistance is now firmly at the forefront of oilseed rape production.

“It is clear the Recommended Lists are shifting towards better phoma and light leaf spot resistance.

“The RL committee has moved the minimum requirement for both diseases up to a 5 and there is talk of that going up to a 6 in the future. I think there is only going to be more of a drive for greater varietal disease resistance in years to come.”

With a 9 for phoma and 7 for light leaf spot resistance, candidate variety InVigor 1030 is evidence of this, adds Ms Middleton.

The candidate variety, which is up for recommendation for the 2017-18 list, is being trialled this season on five farms across the UK.

The role of resistance

One of the trial farmers is Cambridgeshire Fenland grower Rex Heading, who is growing InVigor 1030 under farm conditions, alongside 26ha of mostly Harper and a smaller area of Elgar.

He sees improved varietal resistance as a crucial part of growing the crop on his 162ha farm.

“As we lose more of the chemicals we need to control disease, resistance will become more important.

“Yield and resistance are now equal factors when choosing our rapeseed varieties. Standing ability is important too, because it is better for combining.”

Phoma is now the second most important disease in oilseed rape, after being overtaken by light leaf spot in the past two years.

Bayer commercial technical manager Darren Adkins lists spray timing flexibility as one key advantage of growing a variety with greater disease resistance.

“Fungicide costs haven’t changed much, but you can afford to spray later now than you would have done historically because of this improved resistance.

“You would be particularly worried about getting your fungicide timing right on varieties with a score of less than 6 for phoma,” he says.

Phoma spores on oilseed rape

Mr Heading says phoma has always posed the biggest risk to his crop, but he explains that in recent years light leaf spot, traditionally perceived as a disease of the North, is becoming more of a problem.

However, he says his crops haven’t suffered too badly with light leaf spot in the past couple of years, putting this mainly down to the 6 rating for his crop of Harper.

But such is the pressure of disease in his part of the country, about 10 miles east of Peterborough, he feels there is little scope for cutting fungicide applications as varietal resistance improves.

“The idea that you can save on your fungicide applications is lovely, but I think you still want to have a full package [fungicide + resistance] to fight disease.”

Instead, he sees resistance being valuable in seasons when there are few opportunities to spray due to wet and windy conditions, as it does offer some protection.

Scottish perspective

There has traditionally been a much greater focus on disease resistance in Scotland, because of the higher pressure. Therefore varieties offering 8s and 9s will be particularly welcomed by Scottish growers.

Scottish disease expert Fiona Burnett says light leaf spot continues to be the dominant disease north of the border, but adds that phoma is being seen more in crops nearer the Scottish border.

“We are seeing more of it, but it still isn’t as damaging to yields as it tends to be in England, or when compared with light leaf spot.”

She notes AHDB data shows there is a good correlation between disease resistance and reliable yields.

She says Scottish oilseed rape growers should opt for varieties with stronger LLS resistance, such as Barbados, Nikita and Alizze, as this will offer more reliable yields than chasing for that extra 1-2% gross output.

“If you get a new variety come along that offers a 2% increase in yield, but isn’t as strong on LLS resistance, that extra output can easily be wiped out by the 15% reduction in yield that a moderate LLS infection can bring,” she argues.

When it comes to the role that strong varietal resistance can play in helping with fungicide costs, Prof Burnett talks of a “sliding scale”.

“You should try to tailor your fungicide plan to the disease resistance of the crop. It depends the season, but if you have an 8 or a 9 for LLS, you may be able to cut your fungicide application back.”

Location does have a bearing on this theory, however, with crops grown in high-risk LLS areas, such as Aberdeenshire, more likely to need a full fungicide package paired with highly resistant varieties, she adds.

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