Significant differences have been identified in the resistance of leading commercial oilseed rape varieties to cabbage stem flea beetle (CSFB) feeding.
Work at the John Innes Centre’s (JIC) entomology growth chamber used the centre’s captive CSFB colony to exclude environmental variations which affect traditional field screening.
It employed methods that have already showed differences in adult flea beetle palatability in a diverse set of historic OSR and other closely-related brassica genetics.
JIC senior scientist Dr Rachel Wells, who is overseeing the latest study, says: “While our original work highlighted potential sources of genetic resistance to CSFB feeding in oilseed rape, until now we had no idea whether variation was present in today’s breeding materials.
“Following our established protocol, we introduced flea beetles, all 21-31 days old, into ‘no-choice’ feeding chambers containing seedlings of each variety. We removed the beetles after 48 hours and recorded the cotyledon damage.”
This varied widely, highlighting substantial differences in palatability. Averaged across three replicates, at 12.2 per cent, the most palatable of the five hybrids screened suffered more than twice the damage of the least palatable at just 5.6 per cent.
The variety showing the least damage in the JIC screening was DK Expedient. Richard Phillips, Dekalb technical specialist says: “We have found much of this tolerance comes from a combination of especially rapid autumn growth allowing it to escape from adult grazing better than many other varieties and notably earlier spring growth than most which limits larval damage. To find it is also clearly less palatable than its peers is icing on the cake.”
Dr Wells adds: “Clearly, there seems to be useful genetic variation present in the current commercial variety pool which can be identified and exploited in combating flea beetle. The extent to which this will help limit adult feeding damage under field conditions remains to be seen. But it is a very promising start.”
The work also confirmed previous studies showing beetle feeding activity declines with age, with younger beetles being far more voracious than older ones.
A project to develop a sustainable solution to cabbage stem flea beetle (CSFB) in oilseed rape has been launched.
With funding from Innovate UK, Crop Health and Protection (CHAP) is working in collaboration with CAB International (CABI), Russell Bio Solutions and H&T Bioseed to provide farmers with an alternative to neonicotinoids by developing formulations of a fungal biopesticide, already identified in previous work by CHAP and CABI.
A focus on end-user engagement will run alongside the development work involving two knowledge transfer workshops to encourage and support adoption of the new technology on-farm.