Early results from the farmer-led Spore Scout campaign have revealed widespread and often severe light leaf spot symptoms in oilseed rape crops across the UK. The findings highlight the urgent need for growers to prioritise genetic resistance when they make variety decisions for the 2026-27 season.

Part of the £2.5m Defra-funded LLS-ERASED project, the Spore Scout initiative asked growers and agronomist to send OSR leaf samples to scientists at the University of Hertfordshire. 

The researchers assessed disease severity on 10-12 leaves from each site before incubating samples to encourage sporulation and isolate the pathogen responsible for the disease.

Professor of plant pathology Yongju Huang said the early results suggested growers should not underestimate the disease when selecting varieties for next season.

"We have seen severe light leaf spot symptoms on many of the leaf samples submitted through the Spore Scout campaign," she said. "Overall, the Scottish samples showed higher levels of disease pressure than those from England, although there were some interesting exceptions.

"For example, the level of disease we observed on the cultivar Crusoe in Edinburgh was similar to that seen in Crusoe samples from Cirencester. Traditionally, we have associated the most severe light leaf spot pressure with Scotland, but these findings suggest significant disease levels are now being seen much further south as well.

"This highlights how disease pressure can vary between seasons, varieties and locations, and reinforces the importance of growers looking carefully at resistance ratings when making variety choices."

Prof Huang said the work would help researchers better understand how pathogen populations differ across regions and how effectively current varieties are performing under field conditions.

"As growers start thinking about drilling plans for autumn 2026, these findings are a timely reminder that genetic resistance remains one of the most important tools for managing light leaf spot," she added. "Choosing varieties with good resistance can help reduce disease pressure and improve the resilience of crops throughout the season."

Of the leaf samples received, 65% produced sporulation suitable for single-spore isolation. Researchers are now working to establish pathogen isolates which will later be tested for pathogenicity as part of the wider three-year project. The results will contribute to future disease forecasting and management strategies.

Tom Allen-Stevens, Oxfordshire farmer and managing director of the British On-Farm Innovation Network (BOFIN), which leads LLS-ERASED said: "The response from growers to the first year of our Spore Scout campaign has been hugely valuable. Every sample submitted is helping build a clearer picture of how light leaf spot is developing across the country. We will be repeating the campaign again in spring 2027 and 2028 to develop our knowledge of this devastating disease further."

LLS-ERASED is funded by Defra's Farming Futures R&D Fund. Led by BOFIN, the project brings together farmers, plant breeders, crop scientists and agronomists to tackle light leaf spot using precision breeding alongside improved disease-management tools.