New OSR Brings Major Disease Control Benefits

That’s the view of ADAS plant pathologist Peter Gladders, who suggests that with tighter farm rotations, and reduced performances from some fungicides, growers need to pay greater attention to in-built disease resistance when selecting varieties.

Speaking at the launch of new rape variety Komando, with top NL ratings for resistance to light leaf spot and phoma, Dr Gladders said that significant disease pressure this season was putting crop yields at risk.

“We are now seeing canker coming in at high levels in crops under stress and as summer temperatures increase, we expect problems from early maturity which will restrict yields,” he said.

Dr Gladders estimated that diseases cost UK rape growers between £40-80 million every year, depending upon the severity of the season.

This year, alongside phoma stem canker, which has been shown to cut yields in trials by 0.7t/ha, light leaf spot will also be a significant yield robber nationwide.

“Some 90% of crops have light leaf spot to some degree and while 60-70% of these only have infection levels of 4% there is plenty of inoculum about. Even areas in the South and West are not immune – so there is little room for complacency.

“We are also seeing 80% phoma stem canker infection in the variety Winner at Rothamsted,” he confirmed.

“While the good news is that dry weather during flowering has cut sclerotinia risks and growers are breathing a sigh of relief, canker and light leaf spot are significant.

“In this high pressure situation, new variety introductions with good polygenic resistance scores are an advantage,” said Dr Gladders.

With an unbeatable combination of disease resistance ratings for both light leaf spot (7) and phoma stem canker (8), United Oilseeds’ commercial manager, Ian Munnery expects Komando to take a 9-10% market share in its first year.

“Working with the breeder and CPB Twyford we’ve fast-tracked multiplication and brought forward the launch of the variety,” he said.

“From National List trials, Komando ticks all the right boxes needed for improved performance on farm – right across the UK.

“In the north, its light leaf spot resistance will come into its own, and in the south, Midlands and east of England, Komando, with the best stem canker ratings available, Komando will be a top performer.

“And, with an average straw height of 155cm it is also just 3cm taller than Castille, producing a manageable canopy that stands well.

“The combined package will help provide growers with the security and confidence needed to continue to produce a 2 million tonne UK crop,” suggested Mr Munnery.

Dr Gladders stressed that alongside variety choice, growers need to adopt sensible rotations and agronomic practices to minimise disease.

“Those 10% of growers, who now drill rape every other year, should expect high levels of spore release leading to cotyledon infection from August onwards.

“With close rotations, some form of incorporation to bury and get rid of plant debris that harbours disease is increasingly important.

“Growers need to be aware that fungicides may not restore yield under a high disease pressure seasons on susceptible varieties.

“We are also increasingly concerned about fungicide resistance. Fungicides are not working as well as they did,” he stressed.

“Resistant varieties may not need treatment under low pressure seasons and you may be able to get away with no fungicide input on Komando in this situation.

“However on a susceptible variety, under high disease pressure you can still lose 2t/ha through not spraying.

“Cultivar resistance is a vital part of disease management offering greater flexibility in spray timings and some potential savings in applications.

“By selecting a variety with a light leaf spot score of 8, compared to 3, growers should be at least £50/ha better off.

“And in a serious disease year each disease resistance point could be worth up to £30/ha – providing three times the response,” said Dr Gladders.