Of the 17 main techniques being employed to manage the cabbage stem flea beetle threat at establishment, four stood out as the most successful in the latest national CSFB management study run this spring by Bayer, ADAS and NIAB with a broad cross-section of UK growers.
Sowing earlier the normal, employing seedbed fertilisers, using vigorous fast-developing hybrids and spreading organic manures were all rated at 6.3 or more on a 0-10 scale of effectiveness by the almost 200 growers involved.
Also rated above 6.0 were minimising tillage and double rolling, while leaving OSR volunteers from previous crops and spraying with insecticides were scored the lowest (Figure 1).
Interestingly, with average score of 5.9, encouraging natural enemies by avoiding insecticides was considered noticeably more effective than spraying with insecticides by growers.
Figure 1: Perceived Effectiveness of Techniques to Manage Adult CSFB (2020/21)
** (0= not effective at all: 9 = very effective)
Source: Bayer National CSFB Management Study (2021)
More effective than insecticides in managing CSFB larvae too were considered to be techniques to encourage natural enemies by avoiding spraying or promoting natural predator habitats, while using varieties with faster or earlier spring development was rated the most effective.
“With an average effectiveness score of 5.9 on the 0-9 scale against 3.9 in 2019/20, growers clearly rated the techniques they employed to manage adult CSFB as more effective this season,” comments Bayer commercial technical manager, James Howat. “A natural observation, perhaps, given the much better overall crop performance seen this season.
“While 42% of growers continued to apply insecticides last autumn, this was much lower than the 67% doing so in 2019, with far more growers than the previous season employing only one or two sprays rather than three or more.
“That this change may owe more to the lower observed CSFB pressure last autumn than anything else, however, is suggested by the fact that they were still being used by almost two thirds of growers with the best performing crops under significant autumn CSFB pressure (Figure 2).
Figure 2: Management Techniques & Better Performance in the Face of CSFB (2020/21)
“The positive association between better performance in the face of CSFB and the use of vigorous fast-developing hybrids and seedbed fertilisers is obvious here too,” Mr Howat notes.
“As is the negative association with higher seed rates.”
So how is this experience affecting grower management intentions for the coming season? As well as showing vigorous, fast-developing varieties and seedbed fertilisers as by far the most popular techniques being planned, the proportion of growers looking to them and four other techniques - long cereal stubbles, organic manuring, OSR volunteer trap crops and companion cropping – is markedly higher than last autumn.
At the same time, higher seed rates are being planned by noticeably fewer growers than this time last year (Figure 3).
Figure 3: Future Techniques Planned to Manage CSFB (2020/21 vs 2020/19)
Source: Bayer National CSFB Management Studies (2020 and 2021)
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Early August drilling is fast becoming the norm across the country to counter CSFB grazing, but higher levels of larvae from earlier drilling need managing.