Cabbage stem flea beetle losses threaten oilseed rape's place in the rotation

In October, AICC reported three quarters of England’s crop already showed evidence of damage from CSFB.

Findings from the survey indicate that England’s OSR plantings could fall by as much as 18 per cent in autumn 2019, with the greatest reduction in areas where CSFB has been historically prevalent.

Counties in the South West are now featuring more highly in the poll than in previous years, reflecting the spread of the pest.

Growers in the South are thought to be most likely to reduce their OSR plantings, with a predicted 20 per cent fall in OSR area in counties including Sussex, Surrey, Hampshire and Oxfordshire.

In both the East Midlands and the South West, plantings could drop by 17 per cent.

In total almost 85,000 hectares of oilseed rape were surveyed across all regions of the UK Larvae count results showed numbers in January were considerably higher than those recorded in December, following a mild winter which allowed populations to overwinter, encouraging further hatching.

Sowing date had less of an effect on CSFB larval numbers come spring than expected according to the survey, with figures showing an even split of overall larval numbers between earlier-sown August crop, and crop sown later in September.

The only exception was in the South West where earlier drilling appeared to be beneficial.

In the field

The high level of damage this season has led to farmers questioning the validity of OSR going forward.

Lincolnshire grower, Andrew Ward destroyed almost half of his 220ha crop of oilseed rape in the autumn and replaced it with wheat after dry conditions stopped the crop getting away from exacerbated CSFB attack, only keeping crop with high yield potential.

He says: “We do not drill OSR early because we find we get less pest pressure by later drilling into October. As long as there is moisture, late drilled rape will grow away from attack, but last year through lack of moisture and flea beetle attack it did not.”

After losing £230/ha on the destroyed crop, Mr Ward plans to cut his oilseed rape area by around 50 per cent next season.

He says: “You always think the crop is going to recover but come harvest, it never has. We cannot keep planting crop not knowing if it will even make it to harvest. No other industry would start manufacturing something without certainty of an end product.”

Mr Ward also has concerns over the effect on bees of a lower OSR area. “OSR has significant biodiversity benefits – compared to the area drilled four years ago, including crop losses, we will be almost 30 per cent down this year. To lose that amount of habitat and pollinating crop for bees is catastrophic.”