Pesticides Not the Sole Culprit in Honey Bee Colony Declines

University of Maryland   PLOS ONE   March 18, 2015

Field-based study shows honey bee colonies are not harmed by realistic levels of exposure to the world’s most common insecticide

Colony declines are a major threat to the world’s honey bees, as well as the many wild plants and crops the bees pollinate. Among the lineup of possible culprits—including parasites, disease, climate stress and malnutrition—many have pointed the finger squarely at insecticides as a prime suspect. However, a new study from the University of Maryland shows that the world’s most common insecticide does not significantly harm honey bee colonies at real-world dosage levels.

The study, which was published March 18, 2015 in the journal PLOS ONE, looked at the effects of the insecticide imidacloprid on honey bee colonies over a three-year period. To see significant negative effects, including a sharp decrease in winter survival rates, the researchers had to expose the colonies to at least four times as much insecticide encountered under normal circumstances. At 20 times the normal exposure levels, the colonies experienced more severe consequences.

The study does not totally absolve imidacloprid of a causative role in honey bee colony declines. Rather, the results indicate that insecticides are but one of many factors causing trouble for the world’s honey bee populations.

“Everyone is pointing the finger at these insecticides. If you pull up a search on the Internet, that’s practically all anyone is talking about,” said Galen Dively, emeritus professor of entomology at UMD and lead author of the study. “This paper says no, it’s not the sole cause. It contributes, but there is a bigger picture.”

Imidacloprid is one of a broad class of insecticides called neonicotinoids, so named because they are chemically derived from nicotine. In tobacco and other related plants, nicotine acts as a deterrent by poisoning would-be herbivores. While nicotine itself was once used as an insecticide, it has fallen out of favor because it is highly toxic to humans and breaks down rapidly in sunlight. Neonicotinoids have been engineered specifically to address these shortcomings.

“Imidacloprid is the most widely used insecticide in the world. It’s not restricted because it is very safe—an order of magnitude safer than organophosphates,” Dively said, drawing a comparison with a class of chemicals known to be highly toxic to nearly all living things.

For the study, Dively and his colleagues fed pollen dosed with imidacloprid to honey bee colonies. The team purposely constructed a worst-case scenario, even at lower exposure levels. For example, they fed the colonies tainted food for up to 12 continuous weeks. This is a much longer exposure than bee colonies would experience in real-world scenarios, because most crops do not bloom for such an extended period of time.

Even at these longer exposure periods, realistic dosage levels of imidacloprid did not cause significant effects in the honey bee colonies. Only at higher levels did the colonies start to have trouble producing healthy offspring and surviving through the winter.

“A lot of attention has been paid to neonicotinoids, but there isn’t a lot of field data. This study is among the first to address that gap,” said Dennis vanEngelsdorp, an assistant professor of entomology at UMD who was not involved in the study. “It’s not surprising that higher levels will hurt insects. They’re insecticides after all. But this study is saying that neonicotinoids probably aren’t the sole culprit at lower, real-world doses.”

Dively and vanEngelsdorp both agree that a synergistic combination of many factors is most likely to blame for colony declines. Climate stress could be taking a toll, and malnutrition could be a factor as well. The latter is a particular concern for industrial bee colonies that are rented to large-scale agricultural operations. These bees spend much of their time eating pollen from one or two crops, which throws their diet out of balance.

“Except for the imidacloprid exposure, our test colonies were treated well,” said coauthor David Hawthorne, associate professor of entomology at UMD and director of education at the National Socio-Environmental Synthesis Center(SESYNC). “They weren’t exposed to additional real-world stressors such as malnourishment or multiple pesticides. Colonies coping with these additional pressures may be more sensitive to imidacloprid.”

Dively, Hawthorne and their colleagues found some evidence for at least one synergistic combination. At the highest dosage levels (20 times the realistic dosage) colonies became more susceptible to Varroa mites, parasites that target honey bee colonies. A mite infestation can cause a whole variety of problems, including viral infections and an increased need for other pesticides to control the mites.

“It’s a multifactorial issue, with lots of stress factors,” Dively said. “Honey bees have a lot of pests and diseases to deal with. Insecticide exposure is one factor among many. It’s not the lone villain.”

In addition to Dively and Hawthorne, study authors included UMD technician Michael Embrey, Alaa Kamel of the U.S. Environmental Protection Agency and Jeffery Pettis of the U.S. Department of Agriculture.

This research was supported by the USDA-ARS Bee Research Laboratory (Cooperative Agreement No. 58-1275-7-364), the Foundation for the Preservation of Honey Bees, the Maryland Agricultural Experiment Station and the U.S. Environmental Protection Agency. The content of this article does not necessarily reflect the views of these organizations.

The research paper, “Assessment of Chronic Sublethal Effects of Imidacloprid on Honey Bee Colony Health,” Galen P. Dively, Michael S. Embrey, Alaa Kamel, David J. Hawthorne and Jeffery S. Pettis, was published online March 18, 2015, in the journal PLOS ONE.

Read at: http://cmns.umd.edu/news-events/features/2877

Fines Totaling $16,000 Issued for Pesticide Applicator and Company Role in Bee Deaths

Beyond Pesticides           November 12, 2014

The Oregon Department of Agriculture (ODA) has issued two civil penalties totaling $16,000 in connection with a pesticide application of imidacloprid, a chemical in the neonicotinoid class of insecticides connected to widespread bee decline, this summer that resulted in the death of nearly 1,000 bees at a Eugene apartment complex. Although ODA is taking actions to address pollinator protection, the frequent and continued occurrence of pesticide-related bee deaths indicates that current laws still fall woefully short of preventing these incidences.

Read more... http://www.beyondpesticides.org/dailynewsblog/?p=14473

Fipronil, Imidacloprid Reduce Honeybee Mitochondrial Activity

Science Daily    Source: Society of Environmental Toxicology & Chemistry  August 6, 2014

New research published in Environmental Toxicology and Chemistryaddresses the effects of two broad-spectrum systemic insecticides, fipornil and imidacloprid, on honeybees. These insecticides are widely used in agriculture, and the authors conclude that fipronil and imidacloprid are inhibitors of mitochondrial bioenergetics, resulting in depleted cell energy. This action can explain the toxicity of these compounds for honeybees.

Scientists are urgently trying to determine the causes of colony collapse disorder and the alarming population declines of honeybees. The cross-pollination services they provide are required by approximately 80 percent of all flowering plants, and 1/3 of all agricultural food production directly depends on bee pollination. As a result, there has been a flurry of research on honeybee parasitic mite infestations, viral diseases, and the direct and indirect impacts of pesticides.

The effects of pirazoles (e.g., fipronil) and neonicotinoids (e.g., imidacloprid) on the nervous system are fairly well documented. Daniel Nicodemo, professor of ecology and beekeeping at the Universidade Estadual Paulista in Dracena, Brazil, and lead author of the study states, "These insecticides affect the nervous system of pest and beneficial insects,ften killing them. Sublethal effects related to insect behavior have been described in other studies; even a few nanograms of active ingredient disturbed the sense of taste, olfactory learning and motor activity of the bees."

A key characteristic of colony collapse disorder is the incapacity of the honey bees to return to their hives, and these disruptions have a direct impact on that ability.

In this study, Nicodemo et al. looked at the effects of fipronil and imidacloprid on the bioenergetics functioning of mitochondria isolated from the heads and thoraces of Africanized honeybees. Mitochondria are the power plants of a cell, generating most of a cell's supply of adenosine triphosphate (ATP), used as a source of chemical energy.

Honeybee flight muscles are strongly dependent on high levels of oxygen consumption and energy metabolism. Mitochondrial oxidative phosphorylation drives ATP synthesis, which is required to contract the muscles during flight. "If something goes wrong, the energy production is impaired," explains Nicodemo. "Similar to a plane, honeybees require clean fuel in order to fly."

Both fipronil and imidacloprid negatively affected the mitochondrial bioenergetics of the head and thorax of the honeybees. While at sublethal levels, insecticide damage may not be evident, even such low level exposure clearly contributes to the inability of a honeybee to forage and return to the hive, which could result in declining bee populations.

Read at: http://www.sciencedaily.com/releases/2014/08/140806154013.htm

Declines in Insectivorous Birds Are Associated With High Neonicotinoid Concentrations

Nature.com      Published online 7/9/14     7/17/14

Recent studies have shown that neonicotinoid insecticides have adverse effects on non-target invertebrate species123456. Invertebrates constitute a substantial part of the diet of many bird species during the breeding season and are indispensable for raising offspring7. We investigated the hypothesis that the most widely used neonicotinoid insecticide, imidacloprid, has a negative impact on insectivorous bird populations. Here we show that, in the Netherlands, local population trends were significantly more negative in areas with higher surface-water concentrations of imidacloprid. At imidacloprid concentrations of more than 20 nanograms per litre, bird populations tended to decline by 3.5 per cent on average annually. Additional analyses revealed that this spatial pattern of decline appeared only after the introduction of imidacloprid to the Netherlands, in the mid-1990s. We further show that the recent negative relationship remains after correcting for spatial differences in land-use changes that are known to affect bird populations in farmland. Our results suggest that the impact of neonicotinoids on the natural environment is even more substantial than has recently been reported and is reminiscent of the effects of persistent insecticides in the past. Future legislation should take into account the potential cascading effects of neonicotinoids on ecosystems.

Read at: http://www.nature.com/nature/journal/v511/n7509/full/nature13531.html?WT.ec_id=NATURE-20140717