What can laboratory studies tell us about potential effects of pesticides on nontarget arthropods populations and communities in the field?

Over the past decades, concern has been increasing over reported declines in aboveground biodiversity on farmland. In many regions, data on the toxicity of pesticides to honeybees (Apis mellifera), but not wider nontarget arthropod (NTA) data, are required for pesticide registration. In Europe, the effects of pesticides on NTAs and honeybees have been the subject of regulatory risk assessment for more than 30 years, resulting in a large database. Although insecticides may be expected to affect NTA populations, solely identifying insecticidal modes of action for further NTA testing would result in redundancy among low-risk testing products and may also exclude other modes of action with potential effects in the field. This study assessed whether the honeybee acute risk assessment could provide any indication of the potential impact and recovery time of NTAs in cropped areas at the field scale and, if so, how it might be used in a tiered testing approach. The hazard quotients (HQs; foliar application rate/LR₅₀) were derived for 151 active substances (32% insecticides, 28% fungicides, 38% herbicides, 2% plant growth regulators) for which toxicity data for established EU Tier 1 NTA indicator species (Typhlodromus pyri, Aphidius rhopalosiphi) and application rate data were available. These HQs were compared with published NTA HQ thresholds indicating the time to recovery of NTA populations and communities in field studies (>1 to >12 months). Using the same application rate data, honeybee acute risk quotient (RQ) and HQ were also determined and compared with NTA HQs and honeybee regulatory thresholds. These comparisons demonstrated that, where required, the current regulatory honeybee acute RQ of 0.4 or honeybee HQ of 50 can provide an efficient screening tier to target NTA testing at those products and uses with potential effects in the field where recovery may exceed 12 months. Integr Environ Assess Manag 2024;20:2326-2333. © 2024 SETAC.