Arthropod Pest Control for UK Oilseed Rape – Comparing Insecticide Efficacies, Side Effects and Alternatives

Abstract

Oilseed rape (Brassica napus) is an important combinable break crop in the UK, which is largely protected from arthropod pests by insecticidal chemicals. Despite ongoing debate regarding the use of neonicotinoids, the dominant seed treatment ingredients used for this crop, there is little publicly available data comparing the efficacy of insecticides in controlling key arthropod pests or comparing the impacts on non-target species and the wider environment. To provide an insight into these matters, a UK-wide expert survey targeting agronomists and entomologists was conducted from March to June 2015. Based on the opinions of 90 respondents, an average of 20% yield loss caused by the key arthropod pests was expected to have occurred in the absence of insecticide treatments. Relatively older chemical groups were perceived to have lower efficacy for target pests than newer ones, partly due to the development of insecticide resistance. Without neonicotinoid seed treatments, a lack of good control for cabbage stem flea beetle was perceived. Wide spectrum foliar insecticide sprays were perceived to have significantly greater negative impacts than seed treatments on users’ health, natural enemies, pollinators, soil and water, and many foliar active ingredients have had potential risks for non-target arthropod species in UK oilseed rape fields for the past 25 years. Overall, 72% of respondents opposed the neonicotinoid restriction, while 10% supported it. Opposition and support of the restriction were largely based on concerns for pollinators and the wider environment, highlighting the uncertainty over the side effects of neonicotinoid use. More people from the government and research institutes leaned towards neutrality over the issue, compared to those directly involved in growing the crop. Neonicotinoid restriction was expected to result in greater effort and expenditure on pest control and lower production (0–1 t/ha less). Alternatives for future oilseed rape protection were then discussed.

The impact of restrictions on neonicotinoid and fipronil insecticides on pest management in maize, oilseed rape and sunflower in eight European Union regions

“…A much‐debated question concerns the impact of the CITF restrictions on productivity and economic outcomes for farmers. Several studies (primarily on OSR in the UK) looked at the potential impact of the restrictions on yield, with results ranging from negative to no effects, depending on the study and the region . In our survey, we asked farmers for yield data for growing seasons before and after the CITF restrictions, which showed small and significant changes after the restrictions in some of the examined regions, but not in others (Table S6).…”

“…39 Our data largely confirm the findings of increased foliar insecticide applications and increased pest pressure. 39,44,45,47,50,51,53,54 One generally very useful source of information on insecticide use in the UK is the PUS data. 56 However, the PUS are not conducted on an annual basis.…”

“…More recently, several studies have started to approach the issue by analysing data on pest management practices from growing seasons after the EU restrictions took effect (2014/2015 and 2015/2016). These studies again have focused almost exclusively on OSR cultivation in the UK; for other countries and crops, little or no evidence is available . The studies of OSR in the UK, as well as two studies in Germany and Hungary, suggest that the neonicotinoid restrictions have had a significant effect on pest management, mostly in terms of increasing the number of foliar treatments with pyrethroids, and also other adaptations such as modifications of the sowing date or seed rate, with some evidence that this costs farmers more time and money.…”

“…These studies again have focused almost exclusively on OSR cultivation in the UK; for other countries and crops, little or no evidence is available. 36,[38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54] The studies of OSR in the UK, as well as two studies in Germany and Hungary, suggest that the neonicotinoid restrictions have had a significant effect on pest management, mostly in terms of increasing the number of foliar treatments with pyrethroids, and also other adaptations such as modifications of the sowing date or seed rate, with some evidence that this costs farmers more time and money. There are also indications of increased pest pressure and reductions in the area of OSR grown, although the evidence regarding yield effects is less clear.…”

Insect pollination as an agronomic input: Strategies for oilseed rape production

“…Oilseed rape ( Brassica napus ) is a key crop in arable systems and its production has increased significantly over the last decades, due to its utility as a break crop and through policy support driven by promotion of biofuel crops (Breeze et al., ). Oilseed rape crops require high application rates of synthetic fertilizer (Rathke, Behrens, & Diepenbrock, ; Rathke, Christen, & Diepenbrock, ) and pesticides (Williams, ; Zhang et al., ) in order to attain maximum yield and quality. However, many varieties also benefit from insect pollination through increased pod set and seed set (Garratt, Coston, et al., ; Hudewenz, Pufal, Bogeholz, & Klein, ; Jauker, Bondarenko, Becker, & Steffan‐Dewenter, ; Jauker & Wolters, ; Manning & Wallis, ; Stanley, Gunning, & Stout, ) and improved crop quality parameters such as seed mass or oil content (Bommarco, Marini, & Vaissiere, ).…”