Early August OSR drilling is fast becoming the norm across the country for its value in getting crops through the challenge of cabbage stem flea beetle challenge, reveals the latest national CSFB management study.
The Bayer study with ADAS and NIAB extended to almost 200 growers this spring in exactly the same way and with a similar response rate to the augural 2019/20 study showed a marked swing to earlier drilling lasty autumn.
Nearly half the 250-plus crops involved were drilled before August 20th compared to less than a third in 2019, with far fewer in the traditional mid-late August slot (Figure 1).
What’s more, the study suggests this trend is set to continue with almost four in every 10 growers planning to drill very early this autumn.
Figure 1: OSR Sowing Timing (2020/21 vs 2019/20)
The 2021 study also clearly shows this move is more than justified by experience, even under the lower CSFB pressure and better establishment moisture conditions recorded last autumn.
“For the second year running, overall crop performance declined with delay in drilling,” reports study co-ordinator, Lizzie Carr-Archer. “A far less challenging establishment season meant the differences in crop survival to harvest were less marked than 2019/20. However, the trend was remarkably similar, with performance from September sowing, in particular, suffering under a period of relatively higher pest pressure and lower moisture levels (Figure 2).
Figure 2: Overall OSR Crop Survival by Sowing Date (2020/21 & 2019/20)
“The relatively poor performance of September drillings was mirrored in the establishment scores given by growers for their various crops. An average score of 6.8 here (on a 0 to 10 scale from crops lost to perfect establishment) contrasted with scores of 8.0 or more for all earlier sowings.
“Once again, though, our study recorded higher levels of CSFB larvae from earlier drilling wherever there was a particular autumn challenge from the pest,” she points out. “Amongst other agronomic consequences, this is something those moving drilling forward need to be especially aware of in their management.”
“Providing there is enough moisture in the ground and you preserve it well enough, early drilling can clearly be a valuable defence against cabbage stem flea beetle. But only if you use a variety well-suited to the slot; resist the temptation to push-up seed rates; and do everything possible to minimise the appeal of crops to migrating flea beetles. Otherwise, you could easily create more problems than you solve.”
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Of the 17 main techniques being employed to manage the CSFB threat at establishment, four stand out as the most successful.