Cabbage stem flea beetle (CSFB) control collaboration

When a big issue arises, everyone wants a solution. An all-too-human response is for everyone to react in their own ways. Although better than nothing, it is not often an efficient route to an industry-wide answer. AHDB pest scientist Charlotte Rowley reveals how the UK has found itself at the heart of a coordinated attack on CSFB.

Last year, we revealed the factors most likely to influence cabbage stem flea beetle (CSFB) pressure in winter oilseed rape (OSR). The ADAS-led research identified 31 factors, including an estimate of the reliability of each effect and an indication of how open each factor is to management.

Of the CSFB pressure factors identified, 20 decreased it, seven increased it and four, on balance, resulted in a neutral outcome. The research team mapped out the key factors across a growing season and used a traffic-light system to indicate those most likely to affect control. Only two received a green light: trap crops and soil conditions during sowing/early establishment. The bottom line is that no non-chemical approach is completely reliable. A combination of tactics is needed to deliver the multiple hammer blows required to suppress CSFB.

Trap crops

Oilseed rape volunteers can act as a trap crop and divert CSFB away from adjacent cash crops. In trials, the approach reduced adult infestation (by up to 88%) and damage (by up to 76%). It also resulted in higher plant populations (by up to 56%) and reduced larval populations (by up to 69%). However, benefits were variable and not always observed.

Soil conditions

Weather strongly influences CSFB life cycle and crop development. If the crop has yet to emerge or is emerging when CSFB arrives, it is highly likely to result in crop damage/death. Therefore, sowing dates and soil conditions – particularly soil moisture during emergence – are critical. However, the accurate prediction of risks remains elusive.

Defoliation

As CSFB larvae are far more likely to be present in leaf petioles than in the stem, managed defoliation also showed some promise. In trials, it reduced larval numbers significantly (by 23–55%), with late defoliation, before stem extension, most effective. Linked on-farm trials found that sheep grazing and topping reduced larval numbers by 51% and 25%, respectively. However, researchers did not detect significant yield increases in crops with reduced larval populations. As the technique requires refinement, this approach was marked as ‘amber’.

Collaboration

To build on the solid leads from the research, we recommissioned ADAS to investigate beetle biology and associated crop damage further. Critically, collaboration is hardwired into this three-year (2020–23) project. This element sees researcher-led on-farm trials test the power of multiple control options. It also taps into a new cross-industry taskforce that will share CSFB data across multiple initiatives – it has been dubbed CSFB ‘SMART’ – ‘Sharing Management and Agronomy Research Tools’.

The cross-industry taskforce

Research partners: NIAB, ADAS, Harper Adams University and Rothamsted Research

Industry partners: United Oilseeds, agrochemical companies, independent and distributor agronomy advisers and plant breeders

Funding partners: Defra and AHDB

The NIAB-led SMART project will also ramp up the number of on-farm trials by giving farmers full control. The three-year project (2021–24) will recruit and support growers to conduct and assess their own trials, as well as share their experiences across the network. By swapping notes, the whole industry will learn from the successes and the failures. The initiative also supports the continuation of national CSFB surveys, for a few more years at least.

The oilseed Yield Enhancement Network (YEN) has also risen to the CSFB collaboration challenge. Moving beyond the traditional yield focus – but retaining its competitive element – it now features an ‘establishment beauty contest’. Last autumn, participants submitted data about establishment practices, plant populations and CSFB damage, as well as crop photos, with three award categories:

• Early-drilled OSR (until 14 August)
• Standard-drilled OSR (15–31 August)
• Late-drilled OSR (1 September onwards)

Once again, this effort will help establish what works and why it works. At its foundation is an AHDB-funded analysis of YEN data that interrogated 151 yields from across 92 farms (2017–19) to better understand the factors affecting yield. CSFB is a key reason why UK OSR production is currently at such a low ebb. By pooling efforts to tackle the pest, we will be in the strongest position to come up with the solutions required to sustain production.