P-9: Companion planting as a method of reducing pest pressure from Psylliodes chrysocephala on winter oilseed rape (Brassica napus)

Abstract: In recent years winter sown oilseed rape (OSR) production has decreased as the result
of loss of control of an insect pest, the cabbage stem flea beetle (Psylliodes chrysocephala L.),
due to the pest developing resistance to pyrethroid insecticides, and the EU ban on the use of
neonicotinoid seed dressings. There is therefore an urgent need to develop and optimise
alternative methods of pest control without synthetic chemistry. The potential of trap crops and
undersown ‘nurse’ companion plants for controlling P. chrysocephala on OSR. were tested in
two experiments. In one experiment the use of trap crops was tested with and without
neonicotinoid seed dressing. In a second experiment a range of companion plants were tested
as a ‘nurse crop’ inter-sown with the OSR. In both experiments the level of adult feeding pest
pressure was assessed during the autumn along with assessments of larval infestation.
Ultimately, due to extreme pest pressure from P. chrysocephala, pigeons and slugs, in the year
of the trials, none of the treatments survived beyond January. However, during establishment
and the early development of the crop, plots sown in association with a trap crop or nurse crop
mix did reduce the level of P. chrysocephala feeding on the crop and prolonged the OSR
survival. Data presented here suggests that companion planting can play an important role in
new agroecosystem design and provision of pest management ecosystem services in sustainable
arable systems.