Parasite-insecticide interactions: a case study of Nosema ceranae and fipronil synergy on honeybee

New study in Nature - Scientific Reports finds strong evidence for pesticide + pathogen hypothesis as key explanation for bee disorders.

ABSTRACT: In ecosystems, a variety of biological, chemical and physical stressors may act in combination to induce illness in populations of living organisms. While recent surveys reported that parasite-insecticide interactions can synergistically and negatively affect honeybee survival, the importance of sequence in exposure to stressors has hardly received any attention. In this work, Western honeybees (Apis mellifera) were sequentially or simultaneously infected by the microsporidian parasite Nosema ceranae and chronically exposed to a sublethal dose of the insecticide fipronil, respectively chosen as biological and chemical stressors. Interestingly, every combination tested led to a synergistic effect on honeybee survival, with the most significant impacts when stressors were applied at the emergence of honeybees. Our study presents significant outcomes on beekeeping management but also points out the potential risks incurred by any living organism frequently exposed to both pathogens and insecticides in their habitat.

Even low doses of insecticides put honeybees at risk

Scientists in France have discovered that honeybees are at a higher risk of dying from infection by Nosema ceranae (N. ceranae) when they are exposed to low doses of insecticides. The results, presented in the journal PLoS ONE, support the theory that combining more N. ceranae with a high pesticide content in beehives could contribute to colony depopulation.

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