The effects of neonicotinoid insecticides on bees has been widely covered in the news recently, with laboratory-based studies suggesting that the chemicals are harmful, and field studies which are much less clear cut. Adding to current knowledge on the topic, new research published in the Journal of Apicultural Research further explores the effects that these chemicals may have on social behavior and learning in honey bees.
In one paper, researchers Nadège Forfert and Robin Moritz of Martin Luther University, in Halle-Wittenberg, Germany, explore the effect of the neonicotinoid thiacloprid on social interactions among honey bee workers. They measured interactions in experimental groups of workers to assess the effects of thiacloprid on social network structure, and the amount of food exchanged among worker individuals.
They found that bees fed with thiacloprid significantly reduced their social interactions, suggesting that foraging bees that encounter high doses of insecticide in the field may be less likely to recruit others to these nectar sources, but they also exchanged more food to other group members, which resulted in a dilution of the contaminated food. This means, although thiacloprid may act to interfere with social network structure, it could also play a role in the dynamics of disease transmission in the colony if pathogens are transmitted via food exchange.
In another paper, Anna Papach and colleagues from the University of Poitier, France look at the effect of exposure of honey bee larvae to the neonicotinoid thiamethoxam and the honey bee brood disease American foulbrood on mortality and cognition. They exposed or co-exposed honey bee larvae to American foulbrood and to sub-lethal doses of thiamethoxam. They found no additive effect between the two stressors on larval mortality, but the results do provide the first evidence of impaired learning and memory in adult bees that had been fed thiamethoxam during the larval stage. They found no alterations in learning and memory in bees after infection with American foulbrood at the larval stage.
Science Director at The International Bee Research Association (IBRA) Norman Carreck says, “These new papers are significant because they fill in some gaps in our knowledge of the effects of neonicotinoid insecticides on social behavior and learning in honey bees. As with previous studies, the question remains as to whether bees experience these effects in the field.”
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