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How are pesticides suspected of contributing to colony collapse disorder?
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colony collapse disorder
A western honeybee (Apis mellifera) forages in Italy.
While no definitive causal link has been established, neonicotinoids—a class of systemic insecticides chemically related to nicotine—are suspected of contributing to colony collapse disorder (CCD) through several mechanisms.123
Because these chemicals are systemic, they are absorbed by plants and transported throughout their tissues, including the pollen and nectar that bees consume. Research suggests that exposure to these pesticides may harm honeybees in the following ways:2
- Behavioral Impairment: Sublethal exposure, particularly to thiamethoxam, has been associated with a decreased ability to navigate and locate food sources, which may explain why bees leave the hive and fail to return.123
- Immune Suppression: Exposure to chemicals like imidacloprid and clothianidin may weaken the bees' immune system, making them more susceptible to diseases and parasites such as varroa mites and Nosema species.23
- Synergistic Effects: Scientists suspect that pesticides may act in combination with other stressors—such as pathogens or poor nutrition—to create a synergistic effect that worsens colony health.13