Neonics Hinder Bees' Ability to Fend Off Deadly Mites

Science Daily Story Source: University of Guelph April 22, 2019

The self-grooming behavior of wild honey bees like these can be affected by pesticides.  Credit: University of Guelph

The self-grooming behavior of wild honey bees like these can be affected by pesticides. Credit: University of Guelph

A University of Guelph study is the first to uncover the impact of neonicotinoid pesticides on honey bees' ability to groom and rid themselves of deadly mites.

The research comes as Health Canada places new limits on the use of three key neonicotinoids while it decides whether to impose a full phase-out of the chemicals.

Published in the Nature journal Scientific Reports, the study revealed that when honey bees are infected with varroa mites and then regularly exposed to low doses of a commonly used neonicotinoid called clothianidin, their self-grooming behaviour drops off.

Without that self-grooming, bees are susceptible to mites that can also carry viruses that can quickly kill, said lead author Nuria Morfin Ramirez, who completed the research along with Prof. Ernesto Guzman, School of Environmental Sciences, as part of her PhD.

"When bee colonies began to collapse years ago, it became clear there wasn't just one factor involved, so we were interested in whether there was an interaction between two of the main stressors that affect bees: varroa mites and a neurotoxic insecticide, clothianidin," said Morfin.

"This is the first study to evaluate the impact on the grooming behaviour of bees."

Neonicotinoids, or "neonics," are the most commonly used insecticides in Canada. They are coated on canola and corn seeds or sprayed on fruit and vegetable plants and trees. But they have also been linked to honey bee colony collapses.

Varroa mites are also contributing to colony collapses and have been associated with more than 85 per cent of colony losses.

The mites kill bees by slowly feeding off their body fat and hemolymph (blood), and can also transmit a virus called deformed wing virus (DWV). One of the only ways bees can protect themselves is to groom aggressively and brush the mites off.

The researchers wanted to know whether the two stressors of pesticide exposure varroa mites were working together to contribute to bee deaths. The research team used bees from U of G's Honey Bee Research Centre and exposed them to a widely used neonic clothianidin, either on its own or along with varroa mites.

They experimented with three doses of clothianidin, all similar to what the bees would experience while feeding on flower nectar of neonic-treated crop fields, but all low enough to be considered sublethal.

"What we found was a complicated interaction between the mite and the pesticide that decreased the proportion of bees that groomed intensively, and affected genes associated with neurodegenerative processes," Morfin said.

Bees exposed to medium level doses of the neonic showed no changes in grooming behaviour, but when they were also introduced to varroa mites, the proportion of bees that groomed intensively was 1.4 times lower compared to the bees exposed to clothianidin alone.

When exposed to the lowest dose of the pesticide, the proportion of bees that groomed significantly dropped. The lowest dose was also linked to an increased level of deformed wing virus -- an effect not seen at the higher doses.

"These results showed a complex and non-additive interaction between these two stressors," said Guzman. "This study highlights the importance of reducing stressors that bees are exposed to, to reduce the risk of disease and consequently colony mortality."

https://www.sciencedaily.com/releases/2019/04/190422112818.htm

Not Just Bumble and Honey: Ground Nesting Bees Impaired by Neonicotinoid Exposure

Beyond Pesticides March 19, 2019

Honey bees and neonicotinoids.jpg

(Beyond Pesticides, March 19, 2019) Research is beginning to explain how systemic neonicotinoid insecticides affect often overlooked species of ground nesting bees. While much of the current scientific literature has focused on the impacts of pesticides to bumblebees and honey bees, a study, Chronic contact with realistic soil concentrations of imidacloprid affects the mass, immature development speed, and adult longevity of solitary bees, recently published in Scientific Reports, confirms that wild, soil-dwelling bees are at similar risk. As policy makers consider ways to protect pollinators, this research finds that uncontaminated soil is an important aspect of ensuring the health of wild, native bees.

“This is an important piece of work because it’s one of the first studies to look at realistic concentrations of pesticides that you would find in the soil as a route of exposure for bees,” said Nick Anderson, co-author of the study. “It’s a very under-explored route, especially for some of the more solitary species that nest in the ground.”

In order to study the impact of neonicotinoids on ground nesting bees, researchers used orchard mason bees and leafcutter bees as proxies, as they are easier to gather and rear in the lab, and have a similar ecology to ground nesting species. Roughly 300 bees of each species were taken into the lab as larva, and exposed every 48 hours to either 7.5, 15, or 100 ppb of the neonicotinoid imidacloprid. A control with no exposure was also established as a baseline. The authors explain that these amounts represent realistic exposure patterns that wild bees are likely to encounter in soil.

Researchers monitored the bees every day until they reached adulthood, recording longevity, development speed, and mass. Results show that male and female bees have different reactions to exposure. Female mason bees subject to the highest concentrations of imidacloprid live much shorter lives than those unexposed, while the authors had difficulty determining effects on male bees due to an equipment malfunction. Male leafcutter bees actually lived longer than control bees, but developed much faster and to a smaller size than bees not exposed to a pesticide. Female leafcutter development appeared to depend on the concentration of exposure, with the 15ppb group developing slower than other treatment levels and the 100ppb group developing two days faster than control bees.

The changes are likely a result of a hormetic response by the pollinators. This is a phenomena that results from exposure to pesticides; changes in development occur in order to compensate for energy the bee diverts into physical and biological protections from pesticide exposure. This has important implications for the long term health of ground-nesting bees. Any change in development that distracts or alters normal functioning can affect fitness in the field.

Previous research on the environmental fate of neonicotinoids shows that they have the potential to remain in soil from 200 days to as long as 19 years. This means that the type of chronic exposure tested in the current study could occur years or even a decade after an initial pesticide application. Although scientific literature on wild pollinators is limited, past research on mason bees revealed 50% reduced total offspring and a significantly male-biased offspring sex ratio.

The pollinator crisis is broader than honey and bumble bees, and extends not only to native, ground nesting bees but also butterflies and birds. The New York Times has identified the precipitous decline in insect populations over the past several decades as an insect apocalypse.

While bombastic “apocalyptic” language may be criticized for stoking panic and fear, even these warnings have been generally ignored by many policy makers, begging the question of what it will actually take in order to get action on this critical issue. We need to protect not only honey bees, but the wide diversity of native pollinators in order to maintain agricultural production, floral resources, and other ecosystem services that enable our environment, and ultimately human civilization to thrive.

U.S. Representatives Earl Blumenauer, Jim McGovern, and the 33 current cosponsors of the Saving America’s Pollinators Act are listening to these warnings, and have introduced legislation that would substantive address the threats pesticides pose to pollinators. But in order for change to happen, we need a significant outpouring of public support in favor of this proposal. Take action today by urging your member of Congress to cosponsor SAPA. And if you’re also interested in working on this issue in your state or local community, contact Beyond Pesticides at info@beyondpesticides.org or 202-543-5450.

All unattributed positions and opinions in this piece are those of Beyond Pesticides.

Source: University of Illinois Press ReleaseScientific Reports (peer reviewed journal)

https://beyondpesticides.org/dailynewsblog/2019/03/not-just-bumble-and-honey-ground-nesting-bees-impaired-by-neonicotinoid-exposure/

Improved Regulation Needed As Pesticides Found to Affect Genes in Bees

EurekAlert From: Queen Mary University of London March 6, 2019

Bumblebee Colony Credit: TJ Colgan

Bumblebee Colony Credit: TJ Colgan

Scientists are urging for improved regulation on pesticides after finding that they affect genes in bumblebees, according to research led by Queen Mary University of London in collaboration with Imperial College London.

For the first time, researchers applied a biomedically inspired approach to examine changes in the 12,000 genes that make up bumblebee workers and queens after pesticide exposure.

The study, published in Molecular Ecology, shows that genes which may be involved in a broad range of biological processes are affected.

They also found that queens and workers respond differently to pesticide exposure and that one pesticide they tested had much stronger effects than the other did.

Other recent studies, including previous work by the authors, have revealed that exposure even to low doses of these neurotoxic pesticides is detrimental to colony function and survival as it impairs bee behaviours including the ability to obtain pollen and nectar from flowers and the ability to locate their nests.

This new approach provides high-resolution information about what is happening at a molecular level inside the bodies of the bumblebees.

Some of these changes in gene activity may represent the mechanisms that link intoxification to impaired behaviour.

Lead author of the study Dr Yannick Wurm, from Queen Mary University of London, said: "Governments had approved what they thought were 'safe' levels but pesticides intoxicate many pollinators, reducing their dexterity and cognition and ultimately survival. This is a major risk because pollinators are declining worldwide yet are essential for maintaining the stability of the ecosystem and for pollinating crops.

"While newer pesticide evaluation aims to consider the impact on behaviour, our work demonstrates a highly sensitive approach that can dramatically improve how we evaluate the effects of pesticides."

The researchers exposed colonies of bumblebees to either clothianidin or imidacloprid at field-realistic concentrations while controlling for factors including colony social environment and worker age.

They found clothianidin had much stronger effects than imidacloprid - both of which are in the category of 'neonicotinoid' pesticides and both of which are still used worldwide although they were banned in 2018 for outdoor use by the European Union.

For worker bumblebees, the activity levels of 55 genes were changed by exposure to clothianidin with 31 genes showing higher activity levels while the rest showed lower activity levels after exposure.

This could indicate that their bodies are reorienting resources to try to detoxify, which the researchers suspect is what some of the genes are doing. For other genes, the changes could represent the intermediate effects of intoxification that lead to affected behaviour.

The trend differed in queen bumblebees as 17 genes had changed activity levels, with 16 of the 17 having higher activity levels after exposure to the clothianidin pesticide.

Dr Joe Colgan, first author of the study and also from Queen Mary University of London, said: "This shows that worker and queen bumblebees are differently wired and that the pesticides do not affect them in the same way. As workers and queens perform different but complementary activities essential for colony function, improving our understanding of how both types of colony member are affected by pesticides is vital for assessing the risks these chemicals pose."

The researchers believe that the approach they have demonstrated must now be applied more broadly. This will provide detailed information on how pesticides differ in the effects they have on beneficial species, and why species may differ in their susceptibility.

Dr Colgan said: "We examined the effects of two pesticides on one species of bumblebee. But hundreds of pesticides are authorised, and their effects are likely to substantially differ across the 200,000 pollinating insect species which also include other bees, wasps, flies, moths, and butterflies."

Dr Wurm added: "Our work demonstrates that the type of high-resolution molecular approach that has changed the way human diseases are researched and diagnosed, can also be applied to beneficial pollinators. This approach provides an unprecedented view of how bees are being affected by pesticides and works at large scale. It can fundamentally improve how we evaluate the toxicity of chemicals we put into nature."

###

Research paper: 'Caste- and pesticide-specific effects of neonicotinoid pesticide exposure on gene expression in bumblebees'. Thomas J. Colgan, Isabel K. Fletcher, Andres N. Arce, Richard J. Gill, Ana Ramos Rodrigues, Eckart Stolle, Lars Chittka and Yannick Wurm. Molecular Ecology.

https://www.eurekalert.org/pub_releases/2019-03/qmuo-irn030519.php