A new Stem Health score is set to help growers identify the best oilseed rape varieties to grow with good resistance against three key yield-sapping stem diseases.

Limagrain arable technical specialist Liam Wilkinson says that keeping stems as green as possible enables crops to reach their yield potential, “so any nitrogen in the crop goes up into seed, maximising yield and oil content”.

See also: Tips on getting the most from clubroot-resistant OSR varieties

There are four key stem diseases in oilseed rape: phoma/stem canker, cylindrosporium (light leaf spot), verticillium wilt and sclerotinia.

However, sclerotinia can be easily managed with fungicides, so the focus is on the other three diseases (see table), which can lead to yield losses of 25%-50% in heavy cases.

Mr Wilkinson says enhanced genetics is the most effective solution.

The breeder has developed a robust classification and assessment of varieties and only the top ones will be labelled with the Stem Health label.

High resistance to all three diseases is mandatory to get the Stem Health label, therefore, only one single weakness leads to exclusion from the Stem Health list.

For example, Limagrain marketing manager Will Charlton points to Wagner, which has good phoma (6) and excellent light leaf spot (7) scores, but its verticillium wilt resistance does not meet the threshold.

“It’s not a bad variety, but growers should avoid growing it on land where verticillium wilt is known to be a problem. That’s why its suited for growing in the north.”

Attica, which is Limagrain’s highest yielding variety on the current Recommended List, does meet the threshold for all three, so can be grown across the UK. Recommended List variety Auckland also carries the label.

Seed is available for drilling this summer and Mr Charlton believes Attica could take up to 10% of the certified seed market share.

Four candidate varieties have also got the Stem Health labels.