Traces of a Neonicotinoid Induce Precocious Foraging and Reduce Foraging Performance in Honey Bees

Abstract

There is increasing worldwide concern about the impacts of pesticide residues on honey bees and bee colony survival, but how sublethal effects of pesticides on bees might cause colony failure remains highly controversial, with field data giving very mixed results. To explore how trace levels of the neonicotinoid pesticide imidacloprid impacted colony foraging performance, we equipped bees with RFID tags that allowed us to track their lifetime flight behavior. One group of bees was exposed to a trace concentration (5 μg/kg, ppb) of imidacloprid in sugar syrup while in the larval stage. The imidacloprid residues caused bees to start foraging when younger as adults and perform fewer orientation flights, and reduced their lifetime foraging flights by 28%. The magnitude of the effects of a trace imidacloprid concentration delivered only during larval stage highlights the severity of pesticide residues for bee foraging performance. Our data suggest that neonicotinoids could impact colony function by imbalancing the normal age based division of labor in a colony and reducing foraging efficiency. Understanding this mechanism will help the development of interventions to safeguard bee colony health.

Imidacloprid markedly affects hemolymph proteolysis, biomarkers, DNA global methylation, and the cuticle proteolytic layer in western honeybees

“…This may be surprising, as our bees were fed with IMD, particularly in the bees fed during the preimaginal stages, though Colin et al (2019) revealed that IMD delivered only during the larval stage strongly influences worker foraging. This requires further study.…”

“…Imidacloprid (IMD) is a widely used neonicotinoid insecticide in agriculture (Simon-Delso et al 2015). Sublethal doses of neonicotinoids impaired larval development, gland and neurobiological functions (Blacquière et al 2012;Henry et al 2015;Mužinić and Želježić 2018), longevity, resistance to biotic and abiotic stress (Van der Sluijs et al 2013;Dively et al 2015), foraging, and orientation (Colin et al 2019;Jacob et al 2019) in honeybee workers. IMD also increased the replacement rate, impaired reproductive traits, decreased body weight in queens (Williams et al 2015;Chaimanee et al 2016), and handicapped the sperm quality of drones (Ciereszko et al 2017).…”

“…To examine these four hypotheses, we fed bees food containing 5 ppb (trace) and 200 ppb (more adverse) field relevent concentrations of IMD (Tapparo et al 2011;Pohorecka et al 2012;Henry et al 2015;Colin et al 2019) and monitored their cuticle/hemolymph proteolytic compounds, hemolymph ALP, ALT, and AST, and DNA global methylation in the free-flying colonies.…”

Pollutants and Their Interaction with Diseases of Social Hymenoptera

“…Immune competence has been shown to be compromised in starved social insects [153,175], stressing the energetic costs involved in mounting an immune response [176]. Thus, reduced foraging performance due to stress-induced impaired cognitive abilities may trigger a cascade of food shortage when lower quantities or quality of resources are collected [20,174,177], or alter the social networks of nursing individuals and impair thermoregulation [43]. The disruption of social networks may also translate into altered grooming behavior, which may increase the susceptibility to pathogens breaking through the barrier of the cuticle, such as fungal entomopathogens, as spores are no longer removed from a nestmate´s cuticle [178].…”

“…Sublethal health effects can translate into more dramatic effects, for example by increasing disease susceptibility [4,[7][8][9][10][11][12][13] or decreasing tolerance towards other stressors, such as land use intensification [14][15][16][17]. In addition, such pollutants are known to negatively affect learning abilities and/or lower activity levels [18][19][20][21][22][23][24], which may compromise insects even further [19,21,25].…”