Study finds neonicotinoids harming bees well below label recommended
Ornamental plant nurseries – with their high concentration of different flowers – are an important food source for pollinators. In fact, the University of California (UC), Riverside entomologists Jacob Cecala and Erin E. Wilson Rankin have counted over 150 species of wild bees in nurseries in California alone.
Despite this, very little research has been done on the impact of pesticides often used in nurseries on these essential insects.
Cecala and Rankin therefore conducted an experiment to see how the use of a common neonicotinoid on ornamentals would impact the solitary alfalfa leafcutting bee (Megachile rotundata). The answer? Many.
When the pesticide was applied at only 30 percent of the recommended rate, it still reduced bee reproduction by 90 percent.
“This result reminds us that while ornamentals are essential resources for solitary bees, we need to be vigilant about how we manage these plants and the chemicals we apply to them,” Cecala told EcoWatch in an e- mail.
The research, published in Proceedings of the Royal Society B last month, was designed to determine how different pesticide management practices in the nursery could help or harm bees. In particular, Cecala and Rankin wanted to know if the amount of water the plants received would make a difference.
“Overall, we don’t know much about how plant management practices in agriculture, especially horticulture, affect solitary bee reproduction,” Cecala said. “To fully understand the impacts of neonicotinoids on pollinators, one also needs to know whether the plants themselves are affected by these chemicals.”
Because neonicotinoids are soluble in water, Cecala believed that watering plants more would reduce the impact of pesticides on bees, according to one UC Riverside Press Release. To test this, he and Rankin introduced bees into ornamentals that had been treated with 30 percent of the labeled dose of a common neonicotinoid and plants that had not been. In each category, some plants were watered more and others less. The pesticide they used was imidacloprid, a neonicotinoid sold under the name Marathon®. It is a pesticide designed for use in nurseries and greenhouses that has been on the market since 1994.
What they found was a surprise, Cecala told UC Riverside. Pesticide-treated plants that had been watered more had less imidacloprid in their nectar, but they were just as harmful to bee foraging and reproduction as the pesticide-treated plants that had been watered less.
Although the study was conducted in the controlled environment of the lab, Cecala said it was likely that nursery pesticides would harm bees outside of the lab as well.
“[W]We have observed very detrimental impacts on the reproduction of solitary bees by applying only 30% of the recommended dose of the insecticide – an applicator would probably follow the dose recommended on the label, ”he said. soon to bloom, there is reason to believe that we would see similar negative impacts on these “real world” bees.
A second Silent spring
The study’s results were not surprising for Daniel Raichel, who is the interim director of the Natural Resources Defense Council (NRDC) the pollinator initiative. Instead, they add to a growing body of evidence indicating that neonicotinoids are extremely harmful, both to bees and to other animals.
These pesticides are a problem for two main reasons, according to Raichel. First, they are “phenomenally toxic,” he told EcoWatch. One to study found that agriculture became 48 times more toxic to insects in the United States between 1992 and 2014, in large part due to the use of neonicotinoids.
“A corn seed treated with neonics may have enough active ingredient to kill a quarter of a million bees or more and a square foot of lawn treated with neonics, at the rate approved by the EPA, may have enough ingredient. active to kill a million bees, ”he said. noted.
Another problem is that neonicotinoids are designed to be taken up by every part of a plant, to “make the plant itself the pesticide,” as Raichel put it. This means that they are also easily absorbed by the environment, spreading through the soil and contaminating wild plants and water bodies.
A growing body of research shows that this spread has negative consequences for insects and other animals that eat them. They were found at delay songbird migration, collapse of fisheries and cause birth defects in white-tailed deer.
“Because neonics are so popular across the country and they are used in the same places year after year, accumulating in the soil and spilling out, entering the water, entering the ecosystem, entering the environment. food, we have a situation that looks like the second Silent spring“said Raichel, referring to Rachel Carson’s classic book on the dangers of DDT.
The importance of native bees
While the study is not surprising, it is important in part because it helps expand the study of neonicotinoids from the most studied honey bees to solitary native bee species.
“This is a groundbreaking study because it is one of the few that examines the use of pesticides in nurseries and the impact on native bees,” Conservation of bees founder and executive director Guillermo Fernandez told EcoWatch.
Native bees are “extremely important”, according to Raichel, both in terms of pollination of wild plants and crops. But they are also very threatened. Of the 4000 species of bees originally from the United States, almost 25 percent of them are threatened with extinction. And the study confirms that pesticides are a major threat.
“Solitary bees represent the vast majority of bee species and the reproductive impact of solitary bees shown in this study is very disturbing,” Center for Biological Diversity Scientist Jess Tyler told EcoWatch in an email. “Solitary species are more exposed to pesticides because each female bee is responsible for its own nest and if it is killed its genetic heritage will disappear. “
Fortunately, the new research also points to solutions. Cecala, Raichel and Tyler both called for improved labeling of pesticides.
“I would like to see more explicit language on product labels about the dangers these insecticides pose to bees, especially solitary bees,” Cecala said. “Although the label says it is ‘highly toxic’ to bees (even though it’s not even on the first page), it only warns the user not to apply it if the bees are currently foraging. Our results highlight that very real threats are posed to bees weeks to months after application, even if the plant was not flowering when the pesticide was applied.
Raichel and Tyler further noted that current labeling rates are clearly too high. Tyler further urged the U.S. Environmental Protection Agency (EPA) to require buffer zones for pollinators and remove application methods that pose the greatest risk of spreading chemicals.
“If there are no mitigation measures that prevent poisoning of wildlife, pesticides should be taken off the market,” he said.
Raichel also advocated for a targeted ban on neonicotinoids in areas where they are not really needed. For example, the NRDC is currently promoting the Bird and Bee Protection Act in New York, which would ban the sale and use of seeds coated with neonicotinoids.
There are also things home gardeners can do to protect native pollinators.
“Although the insecticidal formulation we tested in our study is intended for nurseries and greenhouses, the same active ingredient (imidacloprid) is common in many products intended for use in residential gardens and lawns,” said Cecala. . “If you are a home gardener concerned with ‘saving the bees’, I urge you to carefully inspect the labels of any chemicals you come across in the store and try to avoid applying neonicotinoids altogether.”
Additionally, nursery customers can lobby these companies to protect bees, Raichel advised.
“The more you see homeowners demanding that the plants they buy be chemical-free, you will see the markets move in that direction,” he said.
The problem likely extends beyond nurseries to other non-farm green spaces like golf courses, Fernandez added, which affected users can also influence.
What’s more, he added, home gardeners can do even more to make their gardens more bee-friendly than simply abstaining from pesticides. Suggestions include:
- Plantation of native flowering species.
- Installation of “bee baths” – shallow dishes filled with water and twigs where bees can land while having a drink.
- Keep part of the yard intact, since 70 percent of native bees live in the soil.
Some native bee species have ranges of only a few hundred feet, he noted, which means your backyard could be their “whole world.”
“We can actually make quite a change,” he said.
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