Winter oilseed rape crop losses associated with adult cabbage stem flea beetle activity in autumn 2016 have been estimated at about 5.4 per cent - 31,000ha (76,570 acres) of the national area.
These losses are higher than estimates for autumn 2015 (one per cent) and autumn 2014 (2.7 per cent) of the area and may reflect sub-optimal growing conditions in autumn 2016, according to ADAS, using information supplied by AICC agronomists operating in England and Scotland.
Dry soils and cool conditions, which were often recorded in autumn 2016, are known to impede crop establishment and early development and can compromise the crop’s ability to compensate for pest damage.
AHDB also funded the Fera-led survey of CSFB larvae in 2016/17. The latest data from autumn 2016 and spring 2017 showed reductions in number of larvae per plant compared to the previous year, except for the South West in spring. Generally, pest pressure remains higher than prior to 2014/15.
Unpublished data (Fera Science Ltd) also suggested that the adult beetle population decreased in autumn 2016 compared to autumn 2015, based on yellow water trap catches, which could help explain the lower larvae pressure.
Caroline Nicholls, AHDB research manager, said: “The latest findings provide further evidence that crops need a good start in life to counter beetle pressure.
“Even in relatively low pest pressure years, winter OSR can struggle in conditions that hold back crop development and allow beetles to consume more than the crop can replace.”