Scientists may have the first credible clue to the causes of bee colony collapse disorder

Michael Santo's picture

Two studies released today name a widely used pesticide as the culprit behind bee Colony Collapse, a disorder which has threatened bees’ very existence – and our own food supply.

The class of pesticides called neonicotinoid insecticides were introduced in the 1990’s, and the bees started to die off soon thereafter. Now scientists are suggesting that the pesticides’ removal may be key to restoring the health of bee colonies, a notion which the pesticide industry is already vigorously debating.

While a pesticide lobby said the study used unrealistically high levels of the pesticide, scientists are claiming the level of the chemical was just about what bees would encounter at an average farm.

"Our study raises important issues regarding pesticide authorization procedures," said Mikael Henry, co-author of the first study, which focused on honey bees. "So far, they mostly require manufacturers to ensure that doses encountered on the field do not kill bees, but they basically ignore the consequences of doses that do not kill them but may cause behavioral difficulties."

The study reveals that even though the pesticide does not kill the bees directly, it affects their homing abilities. Such bees were two to three times more likely to die while away from the hive. That "high mortality ... could put a colony at risk of collapse" within a few weeks of exposure, especially in combination with other stressors, the authors noted.

The second study focused on bumble bees, the honey bees’ wild cousins. That study revealed that colonies treated with nonlethal levels of the pesticide "had a significantly reduced growth rate and suffered an 85% reduction in production of new queens" compared to colonies without the pesticide.

"Bumble bees have an annual life cycle and it is only new queens that survive the winter to found colonies in the spring," the study noted. "Our results suggest that trace levels of neonicotinoid pesticides can have strong negative consequence for queen production by bumble bee colonies under realistic field conditions, and this is likely to have a substantial population-level impact."

CropLife America, a pesticide trade group, said that the studies "fail to account for the many real-world factors that impact bee and colony health, and the researchers used unrealistic pesticide dose levels that are not commonly found in practical field situations in agriculture,” in their statement.

The honey bee study focused on an intensive cereal farming system where they are used to pollinate the crops and where neonicotinoid pesticides were used.

The EPA is reviewing both studies, which were published in the peer-reviewed journal Science. The current scientific consensus is that bee colony collapse is caused a complex matrix of interactions among multiple stressors, such as reduced habitat, malnutrition, and chemical use.

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Image Source: Wikimedia Commons

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