Quantifying the impacts of the neonicotinoid restriction on oilseed rape pest control and productivity

Under current EU legislation the use of neonicotinoid seed treatments is banned in oilseed rape (OSR, Brassica napus L.) this has led to increased pest pressure and reduced cropping area of OSR in the UK. One main factor for increased pest pressure is from the cabbage stem flea beetle (Psylliodes chrysocephala) which also exhibits resistance to the only remaining alternative synthetic chemical control licensed in the UK. This thesis will in part examine the implications of the neonicotinoid restriction in pest control in the autumn from P. chrysocephala one of the primary target species for neonicotinoid seed treatments in OSR. Empirical field trials were performed to compare how alternative pest protection practices interact with pest control and crop yield. These were done alongside Neonicotinoid to gain a measure of the benefits of seed treatments. In control experiments undertaken during this thesis the interaction between P. chrysocephala and OSR are explored. Providing evidence that OSR can withstand higher pest pressure than current economic thresholds for insecticide application suggest. The relative effect of multiple pest protection methods were shown to be equal to crop protection and that neonicotinoid seed dressings did not show any observable benefit to OSR over un-treated seeds.