Impacts of a nano-enabled pesticide formulation (nTiO2-coated carbendazim) and its constituents on the freshwater snail Lymnaea stagnalis & damselfly Ischnura elegans assessed via in-situ bioassays

Abstract

Novel pesticidal products in which active substances are delivered via nanoscale carrier systems have been suggested to offer functional and environmental benefits over conventional pesticide formulations. Nevertheless, non-target impacts associated with such nano-enabled pesticides remain largely unexplored. The current study compares effects from a nano-TiO2-coated formulation of carbendazim (i.e., nTiO2-coated carbendazim) with those of its active substance (i.e., the fungicide carbendazim), coating material (i.e., nanoscale TiO2), and a treatment in which the latter two are combined, by means of in-situ bioassays. Bioassays focused on the freshwater snail Lymnaea stagnalis and larvae of the damselfly Ischnura elegans, two invertebrate species representing different niches. For L. stagnalis, effects on survival, growth, and feeding were assessed over 29 days, and resource utilization rates of microbial communities present on its provided food source were analyzed to determine feeding-related indirect effects. For I. elegans, survival, feeding, emergence (i.e., development into imagines), and body size upon emergence were assessed over 57 days. Mortality rates of L. stagnalis increased by ∼40 % in nTiO2 and ∼50 % in combined (i.e., carbendazim & nTiO2) treatments applied at environmentally realistic concentrations, but insignificantly in nTiO2-coated carbendazim treatments. We argue that differences in this regard are likely to have arisen from contrasting photocatalytic activity of the nTiO2 utilized in respective treatments. Microbial community carbon utilization profiles exhibited minimal differences between treatments. I. elegans survival, feeding and growth rates were unaffected, but a slight decrease in emergence time was observed across treatments. The findings of the current study highlight that photocatalytic properties of nanomaterials can be an important factor for consideration regarding non-target impacts of nano-enabled products with agricultural applications.