07
Dec
One Single Neonic Exposure Saps Wild Pollinator’s Ability to Reproduce
(Beyond Pesticides, December 7, 2021) One exposure. That’s all it takes for wild bees to experience declines in reproduction and population growth from neonicotinoid insecticides, according to research recently published in the Proceedings of the National Academy of Sciences (PNAS). This incredible sensitivity is exactly the sort of process that could rapidly drive pollinator species into extinction. It is the sort of finding that one would expect government agencies tasked with protecting the environment to discern. Yet, regulators at the U.S. Environmental Protection Agency’s (EPA) Office of Pesticide Programs have consistently failed to listen and meaningfully respond to the latest science. As this is done, the agency is fully aware that ever more pollinators are slated for endangered status, jeopardizing our agricultural economy, ecosystem stability, and the joy we all gain from watching our favorite pollinators flit about the landscape.
Over the course of two years, researchers established a crossed experiment with ground-nesting blue orchard bees (Osmia lignaria). These pollinators, native to North America, overwinter and nest in narrow holes or tubes, making them particularly sensitive to ground-based pesticide applications. Researchers conducted their study during the first year by exposing a group of larval bees to the neonicotinoid imidacloprid through a ground drench at the highest rate on the label for the product AdmirePro, produced by Bayer. Another group was left unexposed. Then, during the second year, some of the unexposed adults were dosed with the same rate of imidacloprid.
Orchard bees exposed to imidacloprid as adults during year two were 4% less likely to initiate nesting, and when they did, they created their nest 38% percent slower, and produced 30% less offspring than those left unexposed. This population also produced 49% fewer female offspring than unexposed bees. Larval bees that were exposed during year one, and subsequently established nests during year two also laid significantly (20%) fewer eggs. This finding indicates that a single pesticide exposure at a young age can result in effects on overall fitness that extend into adulthood and negatively impact reproductive success. “Pesticide exposure reduces bee reproduction, and exposure in either past life stages, or a previous generation, impacts performance of the adult be in the next year,” said lead author Carla Stuligross to The Guardian. “Especially in agricultural areas, pesticides are often used multiple times a year and multiple years in a row. So this really shows us what that can actually mean for bee populations.”
These results line up almost identically with the findings of a study on blue orchard bees published in April 2021. At the highest exposure rate of imidacloprid produced 40% fewer offspring overall. Nesting activity was similarly reduced by 42% in the 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.
While the dangers that imidacloprid poses to mason bees are now clear, the current study adds a critical dimension to the equation: time. A pesticide used over a year ago can harm pollinators today, from a single exposure. These results add considerable urgency to efforts to stop pollinator declines. Imidacloprid can remain in soil for nearly a year, meaning that even if these chemicals were eliminated today, it could be two or more years before ground-nesting pollinators stop declining.
It is time to scrap and rebuild our nation’s approach to pesticide safety. EPA’s Office of Pesticide Programs is now a shell of its former self, hollowed out by industry flunkies who continue to exchange the future of pollination for the profits of multinational pesticide companies. Help us tell EPA that its failed pesticide program needs a new start. We must also go further. In order to achieve this goal, Congress must act to change the laws that permit this crisis to continue by passing the Saving America’s Pollinators Act. Your voice is also needed for that effort: pollinators and the natural world have no lobbyists – they cannot make campaign donations. They only defense is how much we as humans care about their continued existence, and whether we take action on their behalf as a result.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: The Guardian, Proceedings of the National Academy of Sciences (PNAS)
