13
Apr
“No Pollinator is Safe” — New Evidence of Neonicotinoids Harming Wild, Ground Nesting Bees
(Beyond Pesticides, April 13, 2021) A new study is making it increasingly clear that current laws are not protecting wild, ground nesting bees from the hazards of neonicotinoid insecticides. According to research conducted under a grant from the U.S. Department of Agriculture’s Sustainable Agriculture Research and Education (SARE) projects, Blue Orchard Mason Bees (Osima spp) are at particular risk from pesticide-contaminated soil they use to create their nest. Authors of the study note that with honey bees already in decline, pollination services provided wild managed bees like Mason bees are growing in importance. “Wild bees such as Osmia are becoming increasingly popular as managed pollinators in many systems, as there is growing concern that honeybees may not be able to continue to meet the increasing demands of agricultural pollination if these trends continue,” the study reads.
The study looked at three overarching threats to mason bee populations, aiming to identify risks from pesticide contaminated soil used as a nest, effects on larvae exposed to contaminated soil, and whether female mason bees could determine the difference between contaminated and uncontaminated soil. “Imidacloprid is a neonicotinoid, which is a group of pesticides that are highly toxic to bees,” said Christine Fortuin, PhD, graduate student and lead author of the study. “It has several common uses but my research was focused on the soil-drench application method. This is when it is applied directly to the soil and soaked up through the roots of the tree to prevent beetles and other pests.”
To investigate the risks of neonicotinoid-contaminated soil to mason bees, 120 female bees were separated out into groups and exposed to varying levels of imidacloprid (nil exposure, 50 parts per billion [ppb], 390 ppb, and 780 ppb), representing an unexposed control group, as well as low, medium, and high levels in the environment. This experiment was repeated with varying levels of moisture (20% and 40%) in the soil material used to create the mason bee’s nests. A separate experiment exposed the four-day old larvae of mason bees to similar concentrations of neonicotinoids. A final experiment was conducted providing female mason bees the choice whether to use treated or untreated soil to use in their nests.
The study found no trend to the mason bee’s ability to distinguish between contaminated and uncontaminated soil. Embryos appeared to be particularly resilient to the effects of pesticide exposure. However, female mason bees were harmed by soil contact exposure, with effects on fitness noted at each exposure level. At the highest exposure rate, researchers observed a 66% decline in nesting activity as females produced 40% fewer offspring overall. Nesting activity was similarly reduced by 42% in the medium exposed group. For the lowest exposures at 50 ppb (the equivalent of adding 50 drops of pesticide in a 10,000 gallon swimming pool), the sex ratio for offspring was skewed toward male bees. This group had 50% fewer female bees than the unexposed control group.
Soil moisture has important and surprising implications for toxicity. Soil at 20% moisture shows few effects on the pollinators, but at 40% researchers witnessed over 50% of female Blue Orchard Mason bees dying at every level of exposure.
While researchers note that the study provides evidence on routes to avert risk, such as mulching around areas treated with a toxic pesticide to discourage mason bee access, the evidence is increasingly pointing to the fact that no level of use will be safe for pollinators. Although there is relatively little data specifically focused on the harm neonicotinoids inflict on wild-ground nesting bees, this study is already reinforcing existing results. A study published in late 2020 finds that the additive stress of pesticide exposure and food scarcity leads to significant declines in wild mason bees. Scientists exposed female mason bees to the neonicotinoid imidacloprid and found they produce 42% fewer offspring. This effect is exacerbated when food supplies are also low, reducing reproduction by 57%. Not only are the effects on reproduction similar, the study also finds skewed sex ratios – with those exposed to imidacloprid producing 33% fewer daughters.
A study published in March 2021 finds that another wild, ground nesting bee, the hoary squash bee, initiates 85% fewer nests, harvests 5 times less pollen, and produces 89% fewer offspring than bees not exposed to neonicotinoids. A 2019 study may provide insight into the observed effects. That research looks at the effects on larvae after exposure to imidacloprid, recording alterations in development induced by the pesticide. Contaminated larvae display a variety of morphological changes, indicating a hormetic response, wherein changes in development occur in order to compensate for energy the bee diverts into physical and biological protections from pesticide exposure.
Concerns over the long-term ability for honey bees to meet future pollination needs should not be an overarching consideration in exploring methods to protect mason bees. We must protect all pollinators from the hazards of pesticide exposure. Rather than trying to avert risk through changes to label requirements that limit when, where and how a highly hazardous chemical should be sprayed, we must acknowledge that any amount of a bee-toxic pesticide in the environment has the potential to cause harm which is not yet documented. “No pollinator is safe from the harmful effects of neoincotinoid insecticides,” said Drew Toher, community resource and policy director at Beyond Pesticides. “This understanding demands a precautionary approach that stops the use of any pesticide that present unacceptable hazards to pollinators or else we risk a bleak, pollinator-free future that looks like the farm fields of eastern Kenya,” Mr. Toher continued.
Current laws do not come close to implementing such an approach. The Saving America’s Pollinators Act would begin to turn the tide in favor of pollinator protections, but it faces an uphill battle in Congress that requires strong advocacy to move forward. In the absence of a precautionary route to protect pollinators, we must continue to push local, state, and federal leaders to embrace meaningful changes.
Help Beyond Pesticides educate and build the movement that will bring long-needed protections to pollinators and the wider environment by attending the National Pesticide Forum this spring. Cultivating Healthy Communities will bring together expert scientists, farmers, policymakers, and activists to discuss strategies to eliminate harms from toxic chemical use in favor or non-toxic organic solutions. It begins with a pre-conference session on Monday, May 24, and continues every Tuesday beginning May 25, June 1, June 8, and ending June 15, 2021. Registration is open today and available through the webpage on this link.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Sustainable Agriculture Research and Education press release, Project final report
