Toxicopathological determination of safe dose ranges of neonicotinoids for honey bee colonies
Assess the teratogenic (developmental) effects of incremental doses of three types of neonicotinoids on larvae/pupae of workers, queens and drones. Assess reproductive fitness of queens and drones exposed to the incremental doses of three types of neonics. Correlate data generated in objectives one and two to overwinter survival of honey bee colonies exposed to incremental doses of three types of neonics to determine their safe dose range.
The agriculture industry faces the daunting challenge to produce food for an ever-growing world population. Three quarters of the leading global food crops and one third of the total global production volume are dependent upon insect pollination. The honey bees are the most economically important pollinators; however, recent declines in honey bee population may compromise agricultural sustainability and profitability. Unfortunately, the widespread use of neonicotinoids preceded the substantial increase in mortality of honey bees. Accordingly, exposure to neonicotinoids was proposed to play a role in colony collapse disorder (CCD) in honey bees. However, there is much controversy over the true impact of neonicotinoids on honey bee health. The overarching goal of this research project was to attempt to determine the safe dose range of neonicotinoids for honey bees by evaluating effects of neonicotinoids on teratogenicity (developmental effects), gonadotoxicity (reproductive pathology) and reproductive fitness, and on overwinter survival of honey bees.
Considering results of all studies performed in our laboratory, we found that honey bee colonies are resilient even when exposed to relatively high doses over a prolonged period of time. Most resilient are larvae and pupae of workers and drones while larval/pupal stages of queens are most susceptible. Conversely, adult drones are most susceptible to neonicotinoid exposure whereas adult queens are the most resistant.
Based on our studies it appears that honey bee colonies can tolerate environmental neonicotinoid contamination of nectar and pollen up to 5-10 ng/g. Chronic exposure to 20 ng/g of neonicotinoids, which represent high environmental dose reported in Saskatchewan by Codling at al 2016, had negative effects on honey harvest and population of bees in exposed colonies. The same dose increased over winter mortality by 15% when compared to control untreated colonies.
Codling at al (2016) reported that Saskatchewan honey and pollen is at least 5 to 10 times more contaminated by neonicotinoids then the honey and pollen tested anywhere else in the world. This is actually quite concerning, because these high concentrations reported in Saskatchewan demonstrated negative effects on various parameters in our studies. At the same time, it is an undisputable fact that honey bee colonies rapidly expand and flourish on vast Saskatchewan canola fields collecting the highest honey harvest per colony in Canada. Obviously, there is a big discrepancy between Codling’s report and the record honey crops on Saskatchewan canola fields.
Accordingly, the major recommendation to the industry is to perform a large and sound scientific study that will document accurately the levels of neonicotinoid residues in honey and pollen collected from Saskatchewan canola fields. These evidence-based data will be useful for policy makers, canola producers, beekeepers, and consumers.