Over 70 per cent of oilseed rape crops drilled before August 21 will be taken to harvest this year, compared to less than 50 per cent of those drilled after August 31.
This is according to a study by Dekalb conducted in April of this year outlining grower experiences of cabbage stem flea beetle and moisture - the two major challenges for oilseed rape establishment.
“However, these results are not simply calendar date, but were more related to CSFB pressure and moisture levels, with both challenges far more intense from mid-August,” said Edward Hagues, Bayer campaign manager.
On average, 67 per cent of crops survived to the spring and 61 per cent will be taken to harvest, according to the survey of 223 growers.
Major variations in results were recorded by region and drilling date, with survival to harvest hitting over 70 per cent in the North of England.
Three techniques were identified as improving overall crops survival - using varieties with faster or earlier spring development; vigorous, fast-developing hybrids; and spreading organic manures.
Companion cropping also scored well, although the sample size of growers using this technique was smaller.
Mr Hagues said: “Few, if any, associations were found between establishment regime and crop success.”
Hybrids required less re-drilling and survived better than conventional varieties, with almost 9 per cent more hybrid crops reaching harvest.
Dr Sarah Kendall, ADAS crop physiologist, added that early drilling can reduce CSFB adult damage if it means crop emergence does not coincide with the pests arrival.
She said: “Mid-late September drilled crop often have lower larval populations in autumn and spring – this is important when thinking about the larvae as well as the damage done by the adults.
“Getting that soil moisture is really critical, as well as soil to moisture contact. In some cases, it’s better to delay drilling in dry conditions, to give the crop more of a chance, especially in high CSFB situations. Late September drilling dates have a much lower larval burden per plant.”
ADAS studies have found that increasing seed rates does not consistently reduce adult feeding damage, and the proportion of plants is likely to be lost even at high seed rates, Dr Kendall added.
“Small increases might be useful in managing risk for sub-optimal plant populations.”
Trials in East Yorkshire found that for mid-September drilled OSR, the optimum seedrate for the highest yields was 26 seeds/sq.m.
Dr Kendall added: “This shows even in a later sown crop, you can still have very good yields with low plant populations. We are aiming for 25-40 plants/sq.m.”
Launched at Cereals, the Dekalb Farm Innovation Group (FIG) project, managed by ADAS, will explore and test key cabbage stem flea beetle management strategies at a field-scale with growers across the country from this autumn.
The project aims to improve OSR sustainability in the face of CSFB pressures by building on the most successful techniques identified by the 220-plus grower participants in the first-ever national CSFB management study undertaken this spring.
It brings together six growers selected from study volunteers in ADAS-run tramline trials comparing fast developing hybrid, DK Excited with farm standard varieties across a range of establishment regimes and management practices.
The work will be supported by soil moisture measurements at cultivation, drilling and crop emergence as well as assessments of flea beetle pressure, adult damage, establishment success and larval levels.