01
Nov
Bumblebees Shown to Suffer Reproductive Failure after Pesticide Exposure
(Beyond Pesticides, November 1, 2018) A new study offers fresh evidence that wild bumblebee pollinators are particularly vulnerable to the impacts of neonicotinoid (neonic) insecticides, finding that exposure to these compounds interferes with mating success and population stability. Researchers from Worcester Polytechnic Institute in Massachusetts, measuring real-world harms of neonicotinoids, indicate that the impacts they found to bumblebee “reproducers,” namely queen and drone (male) bees, does not bode well for the array of plant species that relies on them. Though advocates warn that destabilizing managed pollinators could threaten U.S. food production and exports, with food prices increasing as cost of bringing pollinators to farms increases, the study’s authors and advocates insist that the impacts of such widespread poisoning of wild bees could be felt well beyond agriculture.
Researchers in the lab compare behavioral and psychological responses of virgin queens, workers, and male Bombus impatiens from multiple colonies to field-realistic doses of the neonicotinoid clothianidin. While every bee was given a replenishing supply of pollen based on body weight and energy demands, four distinct concentrations of diluted analytical-grade (pure) clothianidin (including a control with no pesticide added) were mixed into a nectar-like solution and fed to the bumblebees orally for 5 days. Bees were housed in well-ventilated environmental chambers, with suitable temperature and humidity, and all tests were conducted in red light to minimize additional stress on bees. To ensure tests were field-realistic, researchers sent clothianidin solutions to USDA Agricultural Marketing Service’s National Science Laboratories Testing Division for verification.
After administering the toxicant and recording the bees’ behavior, researchers used gene-specific RNA analysis to test how clothianidin sensitivity and ability to detoxify differed based on sex and “caste” (colony role).
The amount of pesticide-laced sugar solution administered varied by body weight/size, with the queens’ unique role demanding they consume over twice as much solution per day as both workers and males. While field-realistic consumption of clothianidin reduced survival rates in all test bumblebee populations, worker bees showed higher tolerance to chronic oral clothianidin exposure than queens. However, though queens are known to show reduced fertility following neonic exposure, bumblebee males, revealing surprising vulnerability, showed reduced sperm production and 50% mortality at the lowest administered doses.
RNA testing results also revealed even low doses of clothianidin damaged 332 genes associated with major biological functions, including immune system response, learning and memory, locomotion, and reproduction.
Noting the significance of neonic toxicity to the life cycle of wild bees, the consequences of exposure are greatest during bumblebees’ mating and nesting phases. Neonics like clothianidin could be dramatically impacting bumblebee populations by lowering the number of reproducers in late summer and, consequently, the number of queens establishing new colonies the following spring.
“[Neonicotinoids] pose a potential hazard to wild bumblebees at every stage of their annual life cycle” says Robert Gegear, PhD, coauthor of the study, in an interview with Mass Live. “All of these vulnerable points get missed when you focus on bees in an agricultural context.”
With the true trans-generational cost of chemically-dependent land management rarely brought into consideration, many decision makers attempting to regulate pesticides may remain unaware of the unintended consequences stemming from application of systemic toxins.
Federal regulation of neonics is far from effective and at odds with latest independent science. Even in 2018, scientists remain unable to test the total list of ingredients in formulated neonic products, the majority of ingredients remaining undisclosed by chemical manufacturers. Without regulators devoting equal attention to the additional harms of bee-toxic inert ingredients, even this study, using analytical-grade clothianidin, cannot offer a complete measure of neonic toxicity. For many city officials, protecting soil, surrounding ecology, and people will only be considered given persistent grassroots intervention. All the while, people continue applying pesticides in urban and rural areas understanding only a fraction of their full ecological cost.
“As [the] bumblebees and other native pollinators disappear,” says Dr. Gegear, “so too [would] our native flowering plants and the animals that use them for food, shelter, and nesting sites.” Dr. Gegear warns that for toxicity research on wild pollinators to be complete, scientists must note the potential for a destabilization of ecosystem services resulting from reproductive losses among critical wild pollinating species across the globe.
Native plants offer uniqueness to land regions and local watersheds. Without regionally-adapted bumblebees, biodiversity becomes limited, foodchains become destabilized, and ecological niches become vacant, allowing opportunistic “invasive” plant species to flourish. Protecting pollinators is about more than protecting agriculture. Any neighboring native plant or animal species surviving past our front doors is intrinsically reliant on the unsung service provided by pollinators like bumblebees. Their pollination habits enliven the ecosystems interspersed among modern cities and human civilizations throughout history. The areas at risk from a loss of biodiversity are the views we visit on vacations; the stream we sit beside to self-reflect, or catch fish.
Endangered species need protection to support biodiversity and life. Given research showing neonics kill-off bumblebee queens during the critical nest-building period, policy makers must be made aware and take action, or more interconnected species could be lost. With the EPA under the Trump administration heavily influenced by industry, help oppose legislation weakening the endangered species act from sneak attacks. Act locally to insist that your governor ban neonicotinoid insecticides.
Uncover what Dr. Gegear calls the “cascading negative effects that ripple throughout the ecosystem” by learning about trophic cascades and the countless ecological interconnections historically overlooked as part of our industrial growth economy.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: PLOS One
Dear BP, I appreciate your summaries. When you are citing open source literature could you provide the direct link to the source paper? The PLOS One link just takes the reader to the journal so then you have to do additional searching. Thx !
November 1st, 2018 at 10:25 amScott, that is always our aim. The first link in the article should link you to the study. We’ll update the last link to also indicate that. Thank you for bringing that to our attention.
November 1st, 2018 at 12:33 pm