New Study Links Neonicotinoid Pesticide To Negative Social Behavior In Bees

bees neonicotinoids

By Jason Erickson

The plight of the pollinator continues to be documented in an increasing number of studies that have linked neonicotinoid pesticides to a range of negative effects upon bees and their colonies.

Neonicotinoids have been implicated in tens of millions of bees instantly dropping dead at a single honey farm after nearby spraying of GMO crops.  The major producers of these pesticides have also been implicated in false advertising, self-funded studies, and covering up their own negative test results.

While an increasing number of countries, particularly in Europe, have taken action against neonicotinoids, the U.S. stubbornly clings to their widespread use. This is happening even as the bumblebee has been put on the endangered species list in the U.S. for the first time.

A new study has looked beyond what is documented to be a lethal level of pesticide exposure for bees and has found disturbing changes in bee behavior at sublethal levels. These effects, while not as dramatic as millions of bees instantly dropping dead, hint at a more insidious consequence of spraying.

A team of researchers with the Planetary Health Alliance at Harvard University noted that bees exposed to one type of neonicotinoid called imidacloprid experienced dramatic changes in the way they socialized within their hive. Essentially, they abandoned their responsibilities and withdrew from interaction, even with protective care and foraging. My emphasis added:

After tagging, bees were observed before and after exposure to imidacloprid. Crall then evaluated millions of data points to assess behavioral changes among treated bees. He found that bees exposed to the pesticide reduced the frequency of brood care and tended to gravitate towards the perimeter of the nest, becoming less social.

Outside the nest, this neonicotinoid also has significant effects on pollination and foraging behavior. Callin Switzer, a PhD student at Harvard University, worked to study the effects of imidacloprid on pollination behavior. Specifically, Switzer focused on buzz pollination, the ability of bumblebees to forage on and pollinate certain types of plants, using vibrations. Before exposing bees to imidacloprid, Switzer recorded the sound of bees foraging on tomato blossoms. These same bees were then exposed to the neonicotinoid and allowed to resume foraging. However, bees exposed to imidacloprid, at doses similar to those encountered in a single day, were less likely to resume foraging than unexposed bees.

This inability to attend to even the most basic functions that ensure the survival of future generations should sound a new alarm over the potential loss of such a key component of the ecosystem upon which human beings depend.

The researchers leave us with a chilling image based upon their conclusions.

Imagine it’s summer, and in a field by the side of the road, rows on rows of tomato plants wait to be pollinated and produce their delicious fruit. These plants reproduce more following buzz pollination, a service eastern bumble bees are uniquely equipped to provide. However, these tomato plants are covered in imidacloprid, and when bumblebees forage here, they are exposed to sublethal levels of this pesticide. As the season progresses and exposure to imidacloprid increases, bees are still present, but they begin to forage less, don’t care for their young as often, and social interactions change. Outside the nest, a decrease in foraging by affected bumblebees could contribute to lessened crop production and colony food supplies. Within the nest, altered social networks and a decrease in caring for young could lead to population declines in future generations. As the single most important native pollinator species in North America, continued use of the neonicotinoid imidacloprid could have far-reaching effects on the survival of the common eastern bumblebee and the plants they pollinate.


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