OSR CSFB establishment tip: ensure sufficient soil moisture

Cabbage stem flea beetle (CSFB) management in oilseed rape (OSR) requires a combination of approaches. As dry conditions can slow establishment and early growth, make sure soil moisture will be sufficient before sowing.

To induce root emergence, oilseed rape seeds need to take up (imbibe) nearly half (40%) of their weight in water.

Insufficient moisture at and shortly after drilling can reduce germination rates and lead to slow, poor and uneven establishment.

Moisture also supports growth during the crop’s critical early growth stages.

Without sufficient soil moisture, crops will be weakened and less able to tolerate CSFB feeding damage (from adults and larvae).

A survey of over 300 sites (2014 to 2017) quantified the mean percentage leaf area lost (due to adult CSFB feeding) in seedbeds with different soil moisture levels.

Oilseed rape sown into dry soils had a relatively high leaf area loss (just over 25% lost), compared to moist soils or soils with average moisture levels (just over 15% lost).

The survey also showed that crops receiving more than 38 mm of August rainfall had a significant association with reductions in adult CSFB feeding damage.

When conditions were dry after drilling, crops also had a relatively high leaf area lost due to adult CSFB feeding (nearly 25% lost), with a trend towards slightly less leaf area lost when some rain fell after drilling.

Only when there was 'lots of rain' after sowing, did leaf area loss reduce significantly (to about 15% lost).

Although waiting for moisture (present or forecast) before sowing is a good strategy, it depends on uncontrollable forces (i.e. the weather).

Adopting practices that conserve soil moisture offer some insurance.

Ways to conserve soil moisture

• Leave the previous crop's stubble on the soil surface to reduce evaporation*
• Use low disturbance cultivation methods
• Promote good seed-to-soil contact

To improve seed-to-soil contact, roll once and, if possible, twice (at a 90° angle to the first pass).

Poorly consolidated seedbeds are also often cloddy and loosely packed and dry more quickly.

Seedbed compaction can also negatively impact the rate at which seedlings emerge.

*Leaving stubble may also disrupt migrating CSFB from locating emerging oilseed rape and improve natural enemy activity.

Soil type affects the amount of available soil water needed to promote root emergence.

For example, as clay soils have a greater attraction to water, they need relatively high levels of available water content to achieve the amount required for germination (clay soils are also more easily compacted).

For example, soils with 50% clay particles require a moisture content of about 25%. However, a sandy loam soil may only require a moisture content of about 5%.

As many other factors, such as aggregate sizes and seed quality, also affect moisture transfer, the minimum amount of soil moisture needed for successful germination will depend on the site and situation.

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.

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.