Neonicotinoid Pesticide Could Affect Foraging and Social Behaviour in Bumblebees [STUDY]

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Jan 09, 2017 08:00 AM EST

A Chinese farmer spays pesticide on an apple tree on March 25, 2016 in Hanyuan County, Sichuan province, China. (Photo : Getty Images/Kevin Frayer)

A recent study was conducted on bumblebees also known as bombus impatiens, in a plastic, lasercut box blacked out with paint and lit with red light. While the worker bees go about their normal daily activities interacting with fellow adults, others have abandoned their daily patterns and are spending more time in isolation.

They also spend less time caring for the young ones. The chaotic center of bumblebee life, social behavior and interactions within the nest are necessary for bee population health and the reproduction of young ones. The population becomes more susceptible to declines when social interaction and care of younger generation changes.

A postdoc with Planetary Health Alliance at Harvard University, James Crall, a graduate student Callin Switzer and colleagues linked the changes in behavior with sublethal exposure to the neonicotinoid pesticide - imidacloprid.

Crall developed an "automated behavioral tracking system" for the study, which allows a computer connected to cameras within the nest to recognize individual bees and create data points that indicate position and proximity to others.

"Bumblebee nests are not the organized, beautiful geometry of the honeybee," said Crall. Instead, "they're more a hodge-podge of food and larvae in a pile in the middle of the nest space." The automated tracking system allows him to see into the nest.

He acknowledged that the hardest part of the study was the process of tagging each bee, which he described as a race against time to glue on tags before the bees woke up. He added that it was also the slowest part of the experiment as tagging a colony of bees could take days.

The bees were observed before and after exposure to imidacloprid. He evaluated data points in order to assess behavioral changes among treated bees and discovered that bees exposed to the pesticide show reduced care for young ones and also less social interaction, according to Science Daily.

The neonicotinoid also has a substantial impact on pollination and foraging behavior outside the nest. A PhD student at Harvard University, Callin Switzer conducted a study on the effects of imidacloprid on pollination behavior. He focused on buzz pollination - the ability of bumblebees to forage on and pollinate certain types of plants, using vibrations.

He recorded the sound of bees foraging on tomato blossoms before exposing them to imidacloprid and then released them to resume foraging. Callin found that bees exposed to doses of imidacloprid, similar to that encountered in a single day, were less likely to resume foraging than unexposed bees.

Bumblebees are affected by sublethal levels of imidacloprid when they forage on plants covered with the pesticide. However, bees are still present as the season progresses and exposure to imidacloprid increases, but they forage less, care less for their young one and also reduced social interactions.

A reduction in foraging by affected bumblebees outside the nest could contribute to reduced crop production and colony food supplies. Change in social interaction and reduced care for young ones within the nest could lead to a population decline in future generations, according to Newswise.

Persistent use of the neonicotinoid could have negative effects on the survival of the common eastern bumblebee - the most important native pollinator species in North America and the plants they pollinate.

Switzer and Crall will present the findings of their study separately at the 2017annual meeting of the Society for Integrative and Comparative Biology's in New Orleans, Louisiana.

Callin Switzer's research was recently published in Ecotoxicology as "The neonicotinoid pesticide, imidacloprid, affects Bombus impatiens (bumblebee) sonication behavior when consumed at doses below the LD50."

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