OSR CSFB establishment tip: Optimise autumn nutrition

Cabbage stem flea beetle (CSFB) management in oilseed rape (OSR) requires a combination of approaches. Discover how optimised nutrition can support good growth and increase tolerance to pest attack.

When nutrition builds above-ground biomass, it makes crops better able to withstand CSFB feeding pressures.

The AHDB Nutrient Management Guide (RB209) provides guidance on the application of nutrients to OSR in the autumn, either worked into seedbeds as a starter fertiliser or applied as a top dressing.

The application of phosphate and potash to seedbeds is particularly important for soils at Index 0 and 1.

The best approach for nitrogen depends on the emergence date of the crop.

RB209 states that crops sown after early September are unlikely to respond to early nitrogen, as uptake slows during the autumn and into the winter.

Conversely, August-emerging crops take up a relatively high amount of nitrogen, with most stored in the leaves.

Therefore, use sow date information along with RB209 guidance to inform the nutrient management plan.

In autumn 2020, a trial compared the establishment impact of applying poultry manure with artificial nitrogen and no organic amendment.

It found that poultry manure was associated with lower adult CSFB pressures and improved establishment, compared to the other treatments.

The percentage mean leaf area loss was assessed at two timings:

• GS9 to GS10 on 14 September
• GS11 to GS12 on 21 September

At the first timing, significant differences were detected, with poultry manure recording the lowest loss and artificial nitrogen recording the highest loss.

Despite their statistical significance, treatment differences were not large.

For example, the means of the artificial nitrogen treatment and poultry manure treatment were about 10% and 8% leaf loss, respectively.

Additionally, at the second assessment timing, no significant differences were detected. The mean leaf area losses reduced to about 7% across the treatments.

In autumn 2021, a trial investigated the timing of digestate applied to the seedbed and at the time of migration, which, in this trial, was GS11 to GS12.

Once again, this was compared with artificial nitrogen applied to the seedbed.

The percentage mean leaf area loss was assessed at two timings:

• GS10 to GS12 on 16 September
• GS10 to GS14 on 23 September

As the leaf area lost was much higher in the autumn 2021 trials, it provided a stronger test for the treatments.

Once again, significant differences in mean leaf area loss were observed at the first assessment timing.

• Artificial nitrogen: about 27% lost
• Migration digestate: about 25% lost
• Seedbed digestate: about 23% lost

The seedbed digestate treatment continued to be significantly better at the second assessment timing.

The trials indicate that organic amendments may reduce CSFB damage, which could be due to:

• Improved crop establishment and early growth, which reduces percentage leaf area lost
• Making it harder for beetles to locate the crop, such as by masking the smell of the crop

Although the treatment differences were relatively small, CSFB management is about marginal gains.

The small things add up and can make the difference between cropping success and failure.

When applying nutrients, always consider local conditions, comply with relevant rules and regulations and consult a FACTS Qualified Adviser, if necessary.

Due to the complex nature of CSFB, never rely on a single strategy.

Use integrated pest management (IPM) to layer as many techniques as possible to minimise the risks.

This page covers one component of the ‘chase perfection at establishment’ strategy.

Strategy 8 features more information on the use of organic amendments in CSFB management.

The home page also includes information on CSFB Research+, which is generating evidence to further improve strategies.

To view all our CSFB research projects, search ‘CSFB’ on our research page.