Stick to establishment basics to reduce OSR pest pressure through the season

Ensuring strong establishment remains the key challenge in UK oilseed rape production, with growers needing to balance the trade-off between early and later drilling to minimise overall crop risk, says Agrii Seed Key Account and Performance Manager Ian Davy.

While confidence in OSR has improved in many areas, careful establishment planning remains essential, particularly where cabbage stem flea beetle (CSFB) pressure is a concern.

“We have learned a lot about how to grow oilseed rape without neonicotinoids over recent years, and strong-establishing hybrid varieties are really helping growers get their crops away as reliably as possible.

“But while most areas of the UK have had two relatively good years of OSR production, there is little room for complacency. Sticking to the basic rules of establishment is still essential.”

Start with rotation and field choice

The first consideration should be rotation, with OSR grown no more than one year in every five, Ian stresses.

“It is also worth considering block cropping to isolate new crops from old stubbles, while sacrificial headlands can also be considered to limit pest movement.

“OSR volunteers should be left in neighbouring fields to act as a diversionary food source.

“Avoiding ‘green on brown’ is another good policy to follow, with drilling into taller stubble, chaff or green cover preferable over bare soil. Camouflaging the crop confuses CSFB and limits rapid population build-up.”

Balance drilling date with pest and disease risk

Drilling date has been the centre of much attention in recent years. Earlier drilling, particularly in July, is now seen as carrying too much risk and can lead to increased larval damage in the spring, Ian points out.

“There are a number of ways to mitigate the risk of adult damage in the autumn, but not a lot we can do to reduce the effects of larvae in the spring other than choose the right variety in the first place and drill it at the optimum time, when there is sufficient soil moisture.

“In terms of reducing adult CSFB feeding, that probably means waiting for September, which can have its challenges. But drilling five to six weeks earlier than this optimum often means storing up higher CSFB larval loads for the future.

“You are also opening the door to greater disease risk, particularly light leaf spot and clubroot, alongside potential lodging problems and reduced opportunities for controlling blackgrass.”

Whatever the chosen drilling date, if soils are dry, delaying drilling is usually the better option. Minimal soil disturbance can also help conserve available moisture.

Choose varieties for rapid growth and resilience

Rapid-growing hybrid varieties can help crops grow through early CSFB attack, but Ian stresses that there is still no genuine genetic resistance to the pest.

“Selecting varieties with faster growth rates in autumn and spring remains the best policy, as larger plants are more resilient to the effects of larval infestation. However, stick to normal seed rates, as higher seed rates can often be counterproductive.”

Support early rooting and nutrition

Soil conditions should be checked to make sure they are suitable for early growth, with adequate levels of macro and micronutrients, including boron.

“Apply seedbed fertiliser at 30kg nitrogen/ha and 40kg phosphate/ha, ideally in bands, to stimulate root growth.

“Use ammonium nitrate, DAP or Agrii-Start OSR, which is specially formulated by Agrii for OSR. Alternatively, organic manures such as chicken muck or digestate can be used to give the crop an early boost.”

Use companion crops and seed treatments where appropriate

Companion crops can be useful in discouraging CSFB through reduced egg laying and lower overall larval numbers, Ian says.

“Buckwheat is the most widely tested and has been shown to scavenge for phosphate and release this back to the growing crop, but vetches and berseem clover can also be used effectively.”

Seed treatment options, such as Take Off OSR, can also help promote good establishment. Applying a foliar mix of macro and micronutrients at the two-leaf stage can support the crop further.

Monitor crops throughout the season

Ongoing monitoring remains important, particularly at periods when the crop is most vulnerable.

“Look out for shot-holing and use yellow traps to assess pest pressure. Foliar insecticides provide only a weak tool and should be used only as a last resort.”

Growers can get further information on the Agrii 8-point integrated plan for OSR by speaking to their Agrii agronomist or Seed Specialist