Increasing biopesticide use in oilseed rape crops - addressing barriers and realising opportunities

In recent decades, oilseed rape (OSR) has been a profitable break crop in the UK. However, economically important pests, such as peach-potato aphids (Myzus persicae) and cabbage stem flea beetle (Psylliodes chrysocephala), now threaten its viability. Peach-potato aphids transmit yield-limiting viruses such as turnip yellows virus (TuYV) with ~90% efficiency (Schliephake et al., 2000). Alongside cabbage stem flea beetle, they have developed widespread pyrethroid resistance (Bass et al., 2014; Willis et al., 2020). The withdrawal of neonicotinoid insecticides and increasing reliance on pyrethroids have contributed to major losses in OSR, halving its acreage between 2012 and 2020. Additionally, rising temperatures may further bolster pest survival (Hackenberg et al., 2020), underscoring the urgent need for alternative controls.
One potential solution lies in biopesticides, mass-produced agents derived from natural sources (Chandler et al., 2011; Liu et al., 2021). Often termed 'bioprotectants,' they currently account for about 20% of UK-registered insect-control products, mostly used in high-value horticulture (IBMA, 2022; AHDB, 2022). However, their cost (£100-£300/ha) and repeated applications due to limited residual effects (Keswani et al., 2016; Pavela and Benelli, 2016) limit widespread adoption. Large water volumes (e.g., 1500 L/ha) and precise environmental condition application requirements (e.g., dry periods or evenings with higher humidity) further restrict their use (Zaki et al., 2020; Lowenberg-DeBoer et al., 2020).
Comparatively little research addresses how biopesticides could be adapted for OSR, though evidence suggests they could mitigate key pest threats if cost, application frequency and environmental constraints are overcome. This project will optimise biopesticide application by focussing on concentration and frequency to improve feasibility for growers, ultimately aiding sustainable pest management in OSR.