CSFB Research+: Developing a comprehensive programme for cabbage stem flea beetle (CSFB) management in oilseed rape

Abstract

Through an innovative series of studies, CSFB Research+ will develop and promote integrated pest management (IPM) options for cabbage stem flea beetle (CSFB) control in UK winter oilseed rape (OSR). It will generate knowledge and use targeted communications to put it into practice. Since the withdrawal of neonicotinoid seed treatments and the development of widespread resistance of CSFB populations to pyrethroid insecticides, there has been a lack of reliable CSFB control options. This has contributed to a lack of confidence and commitment to the crop, with the UK shifting from a net exporter to a net importer of oilseed rape in recent years. A series of AHDB and Defra-funded projects has improved understanding of the pest’s life cycle, crop risk factors and effective cultural control strategies. In 2025, research evidence underpinned the development of a top 10 list of CSFB management strategies to promote greater uptake of OSR in arable rotations.

Description

Objective 1:

 Provide data on the field performance of novel control products

This objective will evaluate the performance of novel control products against CSFB at various points in its life cycle in field conditions, including those that have already demonstrated potential in controlled environments.

The project team will identify treatments to include in trials, which will run during the first two growing seasons (2025/26 and 2026/27) as a minimum. The treatments will represent a range of product types, such as novel insecticides, botanical biopesticides and entomopathogenic nematodes. A seed treatment has already been identified for testing. As synergists (substances added to plant protection products to improve their performance) may be able to counteract insecticide resistance, these will also be considered.

 

Objective 2:

Extend the cultural control methods available

Fundamental and applied work will develop evidence on the mechanisms of control (including the impact) for a priority set of IPM approaches identified from previous studies.

 

Objective 2a:

OSR stubble cultivation

One of the top 10 CSFB management strategies states ‘stir it up after harvest’ because lightly cultivating OSR stubble soon after harvest may reduce emerging CSFB (according to an initial Defra-funded study). As most CSFB pupae are in the top 30 mm of soil, they are vulnerable to tillage operations.

The work will conduct cultivation trials at two sites in 2025 and 2026, as a minimum, and use CSFB emergence traps to evaluate treatment impact. It will also assess the impact of cultivations on beneficial organisms.

 

Objective 2b:

Brassicas as trap crops

Another top 10 CSFB management strategy says to ‘build brassica buddies’ by using sacrificial strips of brassica (e.g. turnip rape) or OSR volunteer trap crops to lure beetles away from the OSR cash crop.

Previous research shows that leaving OSR volunteers until at least late September reduces adult and larval pressure in nearby OSR fields. Border and in-field strips of turnip rape (which is relatively attractive to CSFB) can also reduce CSFB pressure in OSR. Late-summer-established cover crops containing brassica species may also reduce CSFB pressure in nearby OSR (if trap crops are present during migration).

This work will include studies on brassica-containing cover crops. Initial activity included a survey of farming practices during summer 2025 on the general use of cover/catch crops. The results and stakeholder interviews will guide further work in this area, including the identification of the most commercially relevant approaches and species mixes.

The CSFB research partnership will identify and monitor at least eight catch/cover crops with a high brassica content in 2025/26 and 2026/27, as a minimum, to gather data on their attractiveness to CSFB and the risk of them becoming a source of CSFB in the following year. The latter aspect will consider destruction approaches (techniques and timings).

 

Objective 3:

Improve understanding of CSFB life-history

This objective will generate data to fill knowledge gaps on key CSFB life-history traits, which can be used to develop decision support tools and improve the effectiveness of cultural, biological and chemical control.

Monitoring of CSFB adult migration (funded by AHDB over several years) has created a long-term data set that shows how CSFB migration varies annually and regionally in response to local conditions. Monitoring of the migration in OSR will continue as part of this research (in autumn 2025 and 2026, as a minimum).

In 2024, Bayer CropScience launched an automated yellow water trap (MagicTrap) that catches insects and autonomously identifies and counts contents at regular intervals (using an integrated camera and artificial intelligence). MagicTraps, which have been supplied by Bayer CropScience as an in-kind contribution to the project, will be co-located at the core monitoring sites and used exclusively at several other monitoring sites.

Additionally, a series of experiments will examine the interaction between CSFB development (including larval development) and environmental conditions. As warmer autumns and winters are likely to accelerate many aspects of CSFB development, researching temperature impacts is critical.

CSFB Research+ will also explore the potential to align relevant sources of monitoring data, such as that collected within the Defra Pest and Disease Survey, to provide a single, robust UK data set.

 

Objective 4:

Impact of natural enemies on CSFB control (and how to encourage them)

In the UK, CSFB is a host to two main parasitoids:

Microctonus brassicae, which lays its eggs in CSFB adult beetles, where the parasitoid larvae develop (with the host eventually killed)

Tersilochus microgaster, which lays its eggs in CSFB larvae (within the stem), where the parasitised CSFB larvae drop and pupate in the soil (with the host eventually killed)

Both parasitoids have the potential to contribute significantly to CSFB management. This objective will build on previous studies on the distribution and abundance of M. brassicae in the UK (including parasitisation levels), using yellow water trap contents from project trial sites in the first two years of the project, as a minimum.

The work will also consider site-specific impacts, including the impact of cultivation on both parasitoid species and catch/cover crops on M. brassicae. Ultimately, the research findings will underpin guidance on the management of parasitoid populations to maximise the impact on CSFB.