Insecticides Weakening Honeybees

New research demonstrates how the insecticides fipronil and imidacloprid are depleting the cell energy of honeybees and contributing to colony collapse disorder.

Scientists worldwide are urgently trying to determine the causes of colony collapse disorder and the alarming population declines of honeybees, whose pollination services are critical to 80 percent of all flowering plants, and a third of all agricultural food production.

Daniel Nicodemo, lead author of the new study, states that pyrazoles (e.g., fipronil) and neonicotinoids (e.g., imidacloprid) "affect the nervous system of pest and beneficial insects, often 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 honeybees to return to their hives, and these disruptions have a direct impact on that ability.

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.

In his study, Nicodemo and his colleagues. 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.

source: Society of Environmental Toxicology and Chemistry

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