Results from the 2021 National Cabbage Stem Flea Beetle Management Study confirm
a re
CSFB damage down this se Lizzie Carr-Archer says: “This much improved position results from a combination of noticeably lower autumn cabbage stem flea beetle [CSFB] pressure as well as much better soil moisture conditions at drilling. Intense “Fewer than 20% of the 187 crops in our initial data were judged to have suffered an intense or substantial challenge from flea beetle last autumn against more than 50% in 2019. “At the same time, only around 15% of this season’s crops had to deal with low or very low soil moisture conditions at establishment compared to nearly 40% last season.
National winter OSR crop position SOURCE: National CSFB Management Studies 2020 and 2021
100
Proportion of crops (%)
G
rowers across the country sowing almost 12,000 hectares of winter oilseed rape last autumn report a redrilling rate of just 4% in a benchmarking study run by Bayer in conjunction with ADAS and NIAB in late March/early April. This compares with 14% identified in an almost identical study undertaken at the same time last spring. The survey reveals 90% of crops planted last autumn have survived through to spring and all are being taken through to harvest, against 67% and 61% respectively in 2020 (see graph). Bayer study co-ordinator
90%
90%
80 67% 61%
60 40 20
14% 4%
0
Redrilled
Surviving to spring 2020/21
“For the second year in a row, earlier August drillings gave higher levels of crop survival,” she adds. “The differences between these and
Being taken to harvest
2019/20
later drillings was far less than in 2019, though. “Unfortunately, as ever, some growers have clearly suffered more than most. However, it is
CSFB damage spells double trouble for OSR standing power JCSFB damage weakens stem and restricts growth, rendering crops increasingly prone to lodging, ADAS work has confirmed. ADAS entomologist Fran Pickering says: “It’s long been assumed that CSFB larvae and their activity affect stem strength, but we wanted to know, by how much? And taking
16 AF OSR p16 17 CSFB TR KH MC.indd 2
it one step further, what impact does that have on lodging?” The ADAS field trials took 50 plants at the end of flowering in May 2020 from two sites in East Anglia.
Strength The team assessed the plants’ stem diameter, breaking strength and the internal
damage caused by CSFB. By assessing the percentage area of stem damaged, the plants were sorted into five categories ranging from ‘minimal’ (plants with less than 5% damage), to ‘severe’ (plants with 76-100% of stem area damaged). Ms Pickering says: “There was a clear trend showing thicker stems were stronger
and while this is not news, the results also showed that higher damage was associated with the thinner stems. But why?” The CSFB damage was predominantly mining and browning at the base of the stem and this type of damage restricts the take-up of nutrients and water, which in turn, restricts growth, adds Ms Pickering.
JUNE 2021 06/05/2021 11:36
