A new way to assess the danger that pesticides can pose to bees
Discussing the hazards that different pesticides might potentially pose to bees can be a frustrating and tricky thing. The problem is that risk assessments are done with honey bees. And the honey bee (domesticated, highly social and cavity-nesting) is by no means representative of the roughly 3,999 other bee species in North America (the majority of which are wild, solitary and ground-nesting). Sure, a certain dose of a certain chemical under certain conditions might not kill off a perennial honey bee colony with tens of thousands of individuals. But what would the effect be on a single bee who is alive for only six weeks, raising her brood of eight? A study that was recently published in August might have an answer for us.
Researchers from the University of Guelph and the University of Ottawa looked at the concentrations of three commonly-used neonicotinoid insecticides in the soil at 18 different cucurbit farms in Ontario, Canada. They evaluated the probability that ground-nesting bees – hoary squash bees (Peponapis pruinosa) in this case – would be exposed to a lethal dose of those insecticides while constructing their nests.
"The results were sobering," said Susan Chan, Ph.D. student and lead author, by email. Under many of the scenarios they evaluated, the team found that a hoary squash bee will be exposed to a killing dose of neonicotinoids 80 percent of the time.
"This is really important because we know that bee populations are declining globally but we have never assessed the contribution that pesticides in soil may be making to that decline," said Chan.
Sixty percent of neonicotinoids are applied through seed coatings or as soil applications. Residues can persist in the environment for years, and they've been found in the pollen and nectar that bees consume as both adults and larvae, which is how honey bees can be exposed. However, Chan and her colleagues found the greatest amount of neonicotinoids in the soil, posing a far greater risk than exposure through pollen and nectar combined.
"Our study shows that ground nesting bees are literally risking their lives by excavating their nests in agricultural soil because of the high concentrations of neonicotinoids there,” said Chan. “It is important to remember that not all ground-nesting bees nest in agricultural soil, but many do and those ones are likely at risk."
The toxicity of a substance and the risk it could pose to different forms of life is measured and discussed in terms of median lethal dose (LD50): the average amount of said substance that is required to kill 50 percent of a population in a given amount of time, under specific circumstances. The lower the LD50, the more poisonous it is. Knowing this helps determine how different substances should be handled and used in real-world situations. And this raises an important question regarding pesticides and bees: if the current LD50s for neonicotinoids were determined based on honey bee populations, how accurate and helpful can they be when it comes to assessing the danger these same chemicals pose to other types of bees when they're used on a farm, in a park or around our homes?
Chan thinks the current LD50 for neonicotinoids could indeed be a fair measure: honey bees and hoary squash bees are similar in size, and toxicity through contact varies much less among species than toxicity through consumption. However, because not all ground-nesting bees are as big as a squash bee, and because some pesticides are simply more poisonous to one species than another, Chan recommends dividing the LD50 by ten as a best practice to accommodate the range of bees that exist.
The obvious next step with this new knowledge would be to evaluate any insecticide that is applied to soil for its toxicity on bees that make their homes there. Chan and her colleagues are also in the final stages of completing research into the sublethal effects of contact with pesticides through the soil – because messing up a bee's foraging or reproductive behaviors can be just as problematic for survival as outright death.
“We can no longer glibly ignore soil exposure when it comes to bees,” she said.
Highlight Stories
Here are a few stories that I found particularly interesting since the last newsletter. Thought you might be interested, too.
Investigators look into what caused thousands of bees to die in Spokane neighborhood
(KREM) Bee investigators from the Environmental Protection Agency and the Department of Agriculture arrived this week to begin looking into what caused the rapid die off in the Corbin Park area. Investigators are asking questions to people who live there about what they’ve noticed to try and pinpoint a cause. They suited up, took pictures of the neighborhood, collected some of the dead bees and took samples of hives.
Big buzz about program to turn lawns into pollinator habitat
(Minnesota Public Radio) The Lawns to Legumes program received $900,000 in funding this year from the Legislative Citizen Commission on Minnesota Resources. The initiative aims to help homeowners lawns into pollinator habitat. Over the winter, homeowners will be able to apply for roughly $700,000 in cost share funds for pollinator habitat projects. A priority area for the funding will be where endangered rusty patched bumble bees live.
Microbes on the menu for bee larvae
(Phys.org/USDA) Nature’s famously busy insect isn’t strictly vegan after all. A team of Agricultural Research Service and university scientists has shown that bee larvae have a taste for “microbial meat.” In fact, the team observed an appetite for microbial meat among brood that spanned 14 species distributed across all major families of social and solitary bees—Melittidae, Apidae and Megachilidae among them. The findings underscore the need to examine what effects fungicide use on flowering crops can have on the microbial make up of pollen fed to brood and, in turn, their development. The research on bee larvae consumption of “microbial meat” can be found here.
Scientists buzzing over rare bee discovery in Wisconsin
(WBAY) “Epeoloides pilosulus has garnered a large amount of interest because it is considered one of the rarest bees in North America. Though long suspected to be in the Lakewood area, these are the first confirmed records of the species in Wisconsin since 1910 when it was caught in Dane county.”
Conservation
Planting trees is important for urban pollinator conservation
(Xerces Society) Planting trees is an important action many of us can take to help fight the climate crisis. It’s also an action that will have a significant impact on pollinator conservation. The urban heat island effect, which is caused by large amounts of impervious surfaces, poses serious problems not only for the humans living in urban areas, but for the bee populations living there too. However, trees can provide a signifiant cooling effect in these urban areas that benefit both people and pollinators.
Communities across Connecticut are creating a pollinator pathway for bees and butterflies
(Connecticut Magazine) A grassroots effort, the Pollinator Pathway has spread from town to town with people from land trusts, garden clubs, conservation commissions and watershed associations working with nature centers, municipalities, schools, Scout troops and businesses. Pollinator conservation has not been subject to a lot of political polarization like many other forms of conservation. However, the biggest challenge leaders face is changing the “perfect green lawn” aesthetic. “It looks kind of uninformed and stupid to have a lawn that looks like a golf course. If you have no clover or dandelions, your lawn is a desert.”
Economics
Wildflower strips bring farmers extra money while helping native bees
(Entomology Today) One practice that can bolster native bee populations is planting strips of wildflowers next to crops; however, a study in 2017 found that, without incentives, few farmers choose to plant flower strips. The key to adoption, therefore, is adequate incentives. Researchers examined all the economic costs and benefits of planting wildflower strips and of selling the resulting seeds; their analysis revealed how profit could be made on the sale of seeds.
Policy/Law
MassWildlife: Bald eagles are rebounding, but bumble bees are now endangered
(WBUR) Massachusetts’ Division of Fisheries and Wildlife is proposing an update to its list of endangered, threatened and special concern species to include three bees. The American bumble bee and Walsh’s Anthopora would be listed as endangered, while the yellow-banded bumble bee would be listed as threatened. The state Fisheries and Wildlife Board plans an Aug. 28 public hearing at MassWildlife’s Westborough field headquarters to take feedback on the proposed changes.
Lawsuit challenges EPA’s 200 million-acre expansion of pesticide harmful to bees
(Center for Biological Diversity) The Center for Biological Diversity and Center for Food Safety have sued the Trump administration over its July decision to approve use of the pesticide sulfoxaflor across more than 200 million acres of crops. The approval was granted despite the fact that the Environmental Protection Agency’s own scientists concluded that sulfoxaflor is “very highly toxic” to bees. The decision expands the pesticide’s use to a wide range of crops that attract bees, including soybeans, cotton, strawberries, squash and citrus. The Center’s fact sheet on sulfoxaflor can be found here.
Schumer continues to call for USDA to resume honey bee data collection
(Press-Republican) Speaking at a northern New York bee farm, U.S. Sen. Charles Schumer once again criticized the U.S. Department of Agriculture’s decision to suspend data collection on U.S. honey bee colonies for its annual survey.
Bees are dropping dead in Brazil and sending a message to humans
(Bloomberg) Around half a billion bees died in four of Brazil’s southern states in the year’s first months. The die-off highlights questions about the ocean of pesticides used in the country’s agriculture and whether chemicals are washing through the human food supply — even as the government considers permitting more. Most dead bees showed traces of Fipronil, a insecticide proscribed in the European Union and classified as a possible human carcinogen by the U.S. Environmental Protection Agency.
Science
Bee researchers tackle big questions at this year's BeeCon
(York University) Bee researchers gathered for the annual BeeCon – southern Ontario’s bee researchers symposium – at the end of August to talk about everything related to bees, including bee behavior, genetics and genomics, and conservation. Keynote speaker Ricardo Ayala Barajas of the Universidad Nacional Autónoma de México discussed the diversity of bees in Mexico, as well as the current impact the loss of pollinators is causing. He said there is now a network to study the bees of Meso-America. However, the network still needs more taxonomists to do the work and provide more information about their behavior, habits and floral relations.
Scientists use honey and wild salmon to trace industrial metals in the environment
(EurekAlert/Goldschmidt Conference) Scientists have long known that honey bees pick up small amounts of metal elements when they alight on flowers and leaves. They carry these metals back to the hive where tiny amounts are incorporated into the honey. However, this is the first time researchers have been able to establish clearly the sources of the metals carried by the bees and their products, making them reliable biomarkers for environmental pollution.
Researchers determine pollen abundance and diversity in five major pollinator-dependent crops
(Oregon State University) The study found that almond, cherry and meadowfoam provide ample pollen to honeybees, but highbush blueberry and hybrid carrot seed crops may not. In addition, California almonds don’t provide as much pollen diversity as other crops. The findings are important because a diet low in pollen diversity hurts a colony’s defense system, which consequently increases disease susceptibility and pesticide sensitivity.
Georgia’s first pollinator count will take a census of bees and butterflies
(WABE) Atlanta gardeners say they’re seeing fewer butterflies and lightning bugs. But researchers don’t really know how their populations have changed here. They don’t know how most insects’ populations have changed. The state’s first-ever pollinator census, kicking off this week, could help start to get some answers. It’s a statewide citizen science project, a count of the bees and butterflies that land on flowers in yards, parks and at schools.
What a Virginia wildflower can tell us about climate change
(University of Virginia) “While migration is often viewed as a means for species to proliferate in new environments, in this research we find that there also are inherent perils of expansion, such as a shallow gene pool. While migration will lead to individuals that are better able to reproduce in the small populations expected in new habitats, it may also cause genetic change that limits their ability to survive in the long term.”
Technology
High-tech pollination program begins work in North Dakota sunflower fields
(Agweek) Bee Innovative brought their radar-like technology to North Dakota to see where bees are and where they’re not. Using that data, they work with beekeepers to bring in more bees, strategically placed for where the field hasn’t been pollinated. Bee Innovative has used the technology in Australian blueberry fields and claims increases in both yield and quality.
Everything you need to know about Minecraft’s new bees
(Digital Trends) Fans of Minecraft have a new update to their gaming world: bees. Introducing the new mob should help millions of Minecraft players learn to understand and love what these little insects do for our planet.
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