Abstract
As honeybees are the main pollinator subject to an intense research regarding effects of pesticides, other ecologically important native bee pollinators have received little attention in ecotoxicology and risk assessment of pesticides in general, and insecticides in particular, some of which are perceived as reduced-risk compounds. Here, the impact of three reduced-risk insecticides – azadirachtin, spinosad and chlorantraniliprole – was assessed in two species of stingless bees, Partamona helleri and Scaptotrigona xanthotrica ,w hich are important native pollinators in Neotropical America. The neonicotinoid imidacloprid was used as a positive control. Spinosad exhibited high oral and contact toxicities in adult workers of both species at the recommended label rates, with median survival times (LT50s) ranging from 1 to 4 h, whereas these estimates were below 15 min for imidacloprid. Azadirachtin and chlorantraniliprole exhibited low toxicity at the recommended label rates, with negligible mortality that did not allow LT50 estimation. Sublethal behavioural assessments of these two insecticides indicated that neither one of them affected the overall group activity of workers of the two species. However, both azadirachtin and chlorantraniliprole impaired individual flight take-off of P. helleri and S. xanthotrica worker bees, which may compromise foraging activity, potentially leading to reduced colony survival. These findings challenge the common perception of non-target safety of reduced-risk insecticides and bioinsecticides, particularly regarding native pollinator species.
Highlights
As honeybees are the main pollinator species subject to an intense research regarding effects of pesticides, other ecologically important native bee pollinators have received little attention in ecotoxicology and risk assessment of pesticides in general, and insecticides in particular, some of which are perceived as reduced-risk compounds
IntroductionThe honeybee is perceived as very sensitive to insecticides compared to other arthropod species. 1-3 this species has for some time been the representative model pollinator because it is widely available globally and inexpensive to use as an environmental bioindicator of pesticide pollution. 3,4 a recent meta-analysis study provided support for such use of honeybees, a 10-fold sensitivity ratio correction seems necessary for the extrapolation of insecticide toxicity results from the honeybee to other bee species
The general focus on the impact of neonicotinoids on pollinators, honeybees, has led to an expansion and incentives of reduced-risk pesticides and of biopesticides. 15-18 The encouragement for the use of such compounds is illustrated by European Pesticide Regulation No 1107/2009/EC and Directive 2009/128/EC of the European Parliament and of the Council in addition to similar regulatory efforts in Canada, the USA, and elsewhere. 17,19,20 reduced-risk insecticides may still be highly toxic and represent a high risk to non-target beneficial insects such as stingless bees, which are completely neglected in ecotoxicology and riskassessment studies
Summary
As honeybees are the main pollinator species subject to an intense research regarding effects of pesticides, other ecologically important native bee pollinators have received little attention in ecotoxicology and risk assessment of pesticides in general, and insecticides in particular, some of which are perceived as reduced-risk compounds.
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