Potential Risk to Pollinators from Nanotechnology-Based Pesticides

Abstract

The decline in populations of insect pollinators is a global concern. While multiple factors are implicated, there is uncertainty surrounding the contribution of certain groups of pesticides to losses in wild and managed bees. Nanotechnology-based pesticides (NBPs) are formulations based on multiple particle sizes and types. By packaging active ingredients in engineered particles, NBPs offer many benefits and novel functions, but may also exhibit different properties in the environment when compared with older pesticide formulations. These new properties raise questions about the environmental disposition and fate of NBPs and their exposure to pollinators. Pollinators such as honey bees have evolved structural adaptations to collect pollen, but also inadvertently gather other types of environmental particles which may accumulate in hive materials. Knowledge of the interaction between pollinators, NBPs, and other types of particles is needed to better understand their exposure to pesticides, and essential for characterizing risk from diverse environmental contaminants. The present review discusses the properties, benefits and types of nanotechnology-based pesticides, the propensity of bees to collect such particles and potential impacts on bee pollinators.

Keywords: Bees; Environmental pollution; Exposure potential; Nanotechnology-based particles; Particulate matter; Pesticides; Pollinators.

Figure 1

A honey bee (Apis mellifera) forager, foraging on meadowfoam (Limnanthese alba), a specialty oilseed crop grown in the Willamette Valley of Oregon, USA. Upon close inspection, pollen grains can be seen clinging to the setae (specialized hair-like structures) of the bee.

Figure 2

Electrostatic processes contribute to the movement of pollen from flowers to bees. Specialized structures such as hairs contribute to the bees’ ability to accumulate pollen. Bees also actively collect pollen with their forelegs and mandibles.

Figure 3

Honey bees have specialized structures that collect pollen and other particles. The hair-like structures trap pollen (A), and upon greater magnification much smaller, unidentified particles can also be observed (B–E) collected by other setae and antennal sensilla. Foraging honey bees (Apis mellifera) were obtained from field. Scale as indicated in the figures. Imaging was done at the Oregon State University Electron Microscopy Center using Quanta 600 FEG Scanning Electron Microscope (Thermo Fisher Scientific, Hillsboro, OR, USA).

Figure 4

Scanning electron photographs of various pesticides and pesticide formulations: (A) Optimate CS; (B) Warrior II with Zeon Technology; (C) Natria; (D) Rovral 4F; (E) Tourismo; (F) Protocol; (G) Bravo Weatherstik; (H) Intrepid 2F; (I) and (J) Bayer Advanced All-In-One Lawn Weed & Crabgrass Killer. A larger structure appears to enclose small particles (I); the smaller particles (J) were also observed separately; (K) Tempo SC Ultra and (L) Safari 2SG. Scale has been indicated in the figure plate. Commercially available pesticides in Figure 4 were obtained from local retail establishments, agricultural chemical suppliers, or distributors. Samples were serially diluted with water and pipetted onto a silica substrate, in order to best visualize individual particles. Imaging was done at the Oregon State University Electron Microscopy Center using Quanta 600 FEG Scanning Electron Microscope (Thermo Fisher Scientific, Hillsboro, OR, USA).

Figure 5

Examples of nanotechnology-based pesticide (NBP) formulations. Many NBPs are assembled from one or more pesticide active ingredients and multiple types of macromolecular matrices. (A). Encapsulated formulations; (B). Monolithic Polymeric Spheres; (C). Polymers and hydrogels; (D). Suspension; (E). Porous silica and zeolites; (F). Clays, layered double hydroxides; (G). Metal nanoparticles; (H). Emulsions.

Figure 6

Figure depicts how particles may associate with pollens. (A) Particle as found on pollen collected in California almond orchards during pollination. (B) For comparison, Rovral 4F was applied to a hazelnut leaf using a spray bottle. Almond pollen was collected from orchards in California. Images were acquired on a Quanta 600 FEG Scanning Electron Microscope (Thermo Fisher Scientific, Hillsboro, OR, USA). Scale is 10 μm.

Figure 7

Figure depicts how beebread looks like on a frame. Pollen collected by worker bees is mixed with nectar and fermented by multiple microorganisms into beebread, an essential protein source for developing bee larvae. Nectar is stored as honey, which sustains the colony over the winter. If nanotechnology-based pesticide (NBP) formulations increase accumulation or persistence of pesticides in these compartments, delayed toxicity could result.