Effects of the Ban of Neonicotinoid Seed Treatments on Insecticide Use in Winter Oilseed Rape (Brassica napus L.)

Abstract

Insect pests play a superior role among biotic stresses in winter oilseed rape (Brassica napus L.) production. Thus, the demands for chemical insecticide treatments have been grown. However, insect pest control in winter oilseed rape has become particularly difficult in Europe due to the ban of neonicotinoid seed treatments. This study investigates the on-farm insecticide use to identify the effects of the ban of neonicotinoid seed dressing in Germany. On-farm data of 17 reference farms in Mecklenburg-Western Pomerania (north-eastern Germany) allow a detailed analysis of the insecticide use in winter oilseed rape between 2012–19. Hence, the analyses enable us to compare the insecticide use pattern between the periods before (2012–14) and afterward (2015–19) the ban of neonicotinoid seed treatment. We used the Treatment Frequency Index (TFI) and the Treatment Frequency (TF) to measure the insecticide use intensity. This study provided evidence that insecticide use significantly increased from 2012–19. Insecticide applications have increased by up to 22.5% following the ban on neonicotinoid seed treatments. Farmers’ did treat winter oilseed rape more often with insecticides. Hence, the TF insecticides have risen by 1.1, which means one additional treatment with insecticides at the maximum registered application rate. The autumn insecticide use in winter oilseed rape has been quadrupled. Sowing dates and sowing densities differ between the years, however, we did not find significant trends regarding sowing dates and sowing densities following the ban on neonicotinoid seed treatments. 41% of the reference farms in Mecklenburg-Western Pomerania used the winter oilseed rape seed treatment Lumiposa 625 FS (active ingredient chlorantraniliprole) (2017–19). On-farm uses of the seed treatment Lumiposa 625 FS have increased in this period, however, differs between the reference farms. The current registration of the seed treatment Lumiposa 625 FS in Germany will probably increase the on-farm use in winter oilseed rape.