Developments in non-chemical approaches to cabbage stem flea beetle (CSFB) control were among the topics discussed at the ADAS open days at High Mowthorpe, North Yorkshire. Abby Kellett reports.
Early results from an AHDB-funded project which aims to investigate alternative measures for controlling cabbage stem flea beetle (CSFB) suggest there is potential in trap cropping and defoliation.
The trap cropping work was instigated after earlier research showed when CSFB adults migrate into a crop of oilseed rape, their wing muscles deteriorate and they are no longer able to migrate to another field.
Dr Ellis said: “If correct, this biological quirk means CSFB adults are an ideal candidate for a trap cropping as corralling them into an area which is not going to be cropped with OSR should reduce the pest pressure on emerging rape crops.”
Putting the theory to the test, ADAS sowed two crops of OSR next to a field containing OSR stubble. In one of the adjacent fields, OSR volunteers were allowed to grow for as long as possible, while the other field saw OSR volunteers removed early.
Using yellow water traps, the ADAS team was able to show the adult CSFB population was consistently lower in the OSR crop adjacent to the stubble in which volunteers were retained. There were also about 41% more plants/sq.m at growth stage 12 and about 44% less leaf loss, suggesting volunteer OSR works effectively as a CSFB trap crop.
Since CSFB larvae are likely to be in the leaf petioles before stem extension, ADAS researchers also tested whether defoliation could be used as a method of reducing larval populations.
A crop known to be infested with CSFB larvae was mown in December, January and March and compared with an unmown control field. The March mowing was included to determine if late mowing reduced yield.
Results showed the later crops were mown, the greater the reduction in larval numbers. Mowing in December reduced larval numbers by 31%, mowing in January reduced numbers by 43% and mowing in March reduced numbers by 51%.
Yield assessments confirmed mowing in March after stem extension reduced yield in comparison with unmown plots, but December and January mowing resulted in a higher yield than the unmown control.
Both the trap cropping and defoliation experiments will be repeated in the 2018/19 cropping season.