Tackling Cabbage Stem Flea Beetle is critical for arable farmers to grow a successful oilseed rape crop according to AHDB.
Earlier this month, the Planting and Variety Survey results for the 2024 harvest were published by the levy body, confirming a significant decline in the winter oilseed rape area. Compared to the 2023 harvest, the area may have reduced by up to 21%, dropping to 307,000 hectares, which is potentially the second-lowest crop area in two decades and 59% below the peak area in 2012.
The decline is primarily attributed to record-breaking wet weather and tightening crop margins, with CSFB also playing a role. Despite these challenges, farmers are looking forward to the next crop season, hoping to leverage their experience and favourable weather conditions.
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Key lessons for CSFB Management:
Understanding Migration Patterns
Adult beetles typically migrate into crops from late August to early September, peaking in early to mid-September before declining towards the end of September. This migration pattern identifies late August to mid-September as the highest-risk window for sowing.
Sowing Early
Crops sown before the last week of August can establish well before beetles arrive in significant numbers. Established plants can tolerate substantial feeding damage. For instance, plants at the four-leaf stage can withstand up to 50% leaf area loss if soil moisture is adequate. However, early-sown crops may face higher larval loads due to more opportunities for egg laying.
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Sowing Late
Crops sown from mid-September emerge after peak beetle migration, reducing adult feeding damage. Cooler temperatures associated with late sowing also reduce egg numbers and subsequent larval populations. Selecting a variety with good autumn vigour is beneficial when sowing later.
Sowing Trials and Insights
An ADAS-led trial as part of the AHDB project demonstrated that changing sowing dates by just a few weeks could mean the difference between a total crop loss and a successful yield. The trial used three sowing dates: early August 26, middle September 6, and late September 15. The middle treatment coincided with peak migration and suffered significant damage, while the early and late sowing dates recorded minimal leaf area loss and substantial yields.
Companion Crops
Companion cropping has shown potential in reducing CSFB pressure. Trials indicated that companion crops could consistently produce modest reductions in CSFB numbers, adult feeding damage, and larval populations. Buckwheat, alone or with berseem clover, generally performed best when sown one to two weeks ahead of oilseed rape.
Integrated Pest Management (IPM)
With limited effective chemical options, managing CSFB requires a layered approach using alternative solutions. This series of articles on CSFB IPM aims to provide a solid foundation for experimentation at the farm level, helping farmers grow oilseed rape with more confidence. Farmers are encouraged to share their experiences to build a comprehensive understanding of effective interventions.
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