Understanding the Effects of Sublethal Pesticide Exposure on Honey Bees: A Role for Probiotics as Mediators of Environmental Stress

Abstract

Managed populations of the European honey bee (Apis mellifera) support the production of a global food supply. This important role in modern agriculture has rendered honey bees vulnerable to the noxious effects of anthropogenic stressors such as pesticides. Although the deleterious outcomes of lethal pesticide exposure on honey bee health and performance are apparent, the ominous role of sublethal pesticide exposure is an emerging concern as well. Here, we use a data harvesting approach to better understand the toxicological effects of pesticide exposure across the honey bee life cycle. Through compiling adult-and larval-specific median lethal dose (LD 50) values from 93 published data sources, LD 50 estimates for insecticides, herbicides, acaricides, and fungicides are highly variable across studies, especially for herbicides and fungicides, which are underrepresented in the meta-data set. Alongside major discrepancies in these reported values, further examination of the compiled data suggested that LD 50 may not be an ideal metric for honey bee risk assessment. We also discuss how sublethal effects of pesticide exposure, which are not typically measured in LD 50 studies, can diminish honey bee reproduction, immunity, cognition, and overall physiological functioning, leading to suboptimal honey bee performance and population reduction. In consideration of actionable solutions to mitigate the effects of sublethal pesticide exposure, we have identified the potential for probiotic supplementation as a promising strategy that can be easily incorporated alongside current agricultural infrastructure and apicultural management practices. Probiotic supplementation is regularly employed in apiculture but the potential for evidence-based targeted approaches has not yet been fully explored within a formal toxicological context. We discuss the benefits, practical considerations, and limitations for the use and delivery of probiotics to hives. Ultimately, by subverting the sublethal effects of pesticides we can help improve the long-term survival of these critical pollinators.

Chronic High Glyphosate Exposure Delays Individual Worker Bee (Apis mellifera L.) Development under Field Conditions

“…More recently, however, several laboratory studies reported sublethal effects of the herbicide at the individual bee level. Such effects are of current concern, as they can reduce honey bee reproduction, immunity, cognition, and overall physiological functioning, leading to a suboptimal honey bee performance and population decline [ 15 ]. For GBH, impaired cognitive abilities and navigation skills [ 16 , 17 ], and, primarily, implications for the host-microbiome were indicated [ 18 , 19 , 20 ].…”

Lactobacillus spp. attenuate antibiotic-induced immune and microbiota dysregulation in honey bees

“…Importantly, despite susceptibility or resistance, OTC is unable to treat P. larvae spores in the comb, which can act as a source of reinfection. To address these issues and guard against the potentially rapid evolution of resistance, it is prudent to test alternative control measures, which so far include hygienic breeding 12 , use of bioactive essential oils 13 , bacteriophage therapy 14 , synthetic indoles with anti-germination properties 15 , and supplementation of hives with lactic acid bacteria [16][17][18] . The promise of this latter approach is up-held by studies demonstrating that lactobacilli can promote insect innate immunity and detoxification [19][20][21] , extend longevity of adult honey bees 22 , and stimulate queen brood production 23,24 .…”

Inert agricultural spray adjuvants may increase the adverse effects of selected insecticides on honey bees (Apis mellifera L.) under laboratory conditions

“…Tank mixes can increase total mortality in honey bees in predictable (Pilling & Jepson 1993;Iwasa et al 2004;Wernecke et al 2019) and unpredictable ways Zhu et al 2014;Wade et al 2019). Despite their relevance under normal eld conditions, these aspects of pesticide toxicology are often overlooked (Chmiel et al 2020). Most emphasis has focused on formulations and their active ingredients rather than on the adjuvants that can be added to the spray solution.…”