Oilseed rape recovery hopes grow after pest survey

Low cabbage stem flea beetle larvae levels for a second year have strengthened hopes that UK oilseed rape is beginning to recover after several difficult seasons.

A new stem larvae survey, funded by United Oilseeds and carried out by Niab, found consistently low pest pressure across the vast majority of farms sampled.

The survey asked 100 UK growers to submit 10 oilseed rape stems from each farm during March.

The samples were examined to assess the number of cabbage stem flea beetle larvae present, with each participating grower receiving their own results.

United Oilseeds said the findings were encouraging, with larval numbers remaining low for the second consecutive year.

While some individual sites recorded higher pressure, the national picture was similar to last year and showed far lower levels than those seen during the most challenging CSFB seasons.

The accompanying heat map showed low pest pressure across much of the UK.

United Oilseeds said the survey also highlighted the value of collaboration between growers, researchers and the wider industry.

By volunteering stem samples, growers helped build one of the clearest national pictures of CSFB pressure, providing useful information for both farmers and researchers.

James Warner, managing director of United Oilseeds, said the results should give growers confidence as they plan autumn drilling.

He said: “Seeing low larval numbers for a second consecutive season is genuinely encouraging.

“Combined with stronger crop establishment, improving confidence and positive gross margins, the signs are there for more growers to bring oilseed rape back into the rotation.”

However, Mr Warner warned that growers should not become complacent.

He said: “The important thing now is that we don't become complacent.

“By continuing to adopt practical, research-backed measures such as shallow post-harvest cultivation, we have a real opportunity to keep CSFB pressure low and continue rebuilding a resilient UK oilseed rape crop.”

United Oilseeds said the findings add to a wider sense of optimism around oilseed rape.

The crop area is increasing again, prices have remained steady and gross margins continue to compare favourably with many alternative break crops.

But maintaining progress will depend on continued use of practical measures developed through industry research and collaboration.

The key practical message for growers is the value of shallow post-harvest cultivation, with research led by Colin Peters at Niab showing that cultivating oilseed rape stubbles to around 30mm as soon as possible after harvest can reduce emerging adult flea beetles by 50% to 90%.

The approach works by disrupting the insects as they pupate in the soil, helping to reduce populations later in the summer and lower pressure on following crops.

As evidence has built, shallow post-harvest cultivation has moved up the list of priorities within the OSR Reboot 10 Strategies for Managing CSFB and is now recognised as one of the most effective practical actions growers can take.

The measure remains an important area of work within the jointly funded CSFB Research+ programme, where researchers are continuing to refine and validate best practice.

United Oilseeds said continued use of research-backed measures, alongside knowledge-sharing between growers, researchers, breeders and industry partners, would be key to maintaining progress.