Honeybee Colony Deaths Are Linked to the Number of Pesticides, Not Dosage

A team of researchers has found that exposure to multiple pesticides predicts honeybee colony death rates, regardless of the dosage. The team also found a correlation between colony death and the use of fungicides, including those labeled as being safe for bees. The details are in a paper that was just published in the journal Scientific Reports.

The team studied 91 different commercial honeybee colonies throughout the eastern United States. They measured insecticide, fungicide, and herbicide levels in residues from pollen and wax samples. In total, the team detected the presence of 93 different pesticides. The researchers then analyzed death rates for both colonies and individual queens.

The research team found that as the number of pesticide compounds increased, the risk of death for the colony also increased. The number of unique pesticides predicted colony death more than the individual doses. The team also found that the presence of fungicides increased the chance of death for a honeybee colony. This included fungicides that are normally considered safe for bees. The most dangerous fungicides were ones that disrupted sterols to kill fungi.

The team speculates that the presence of multiple pesticides interferes with the bees’ ability to metabolize the toxins. They also found that colonies with a high number of pesticides tended to lose at least one queen a season. The colonies with the lowest pesticide concentrations didn’t lose queens and had no major death events.

These new findings suggest that the number of pesticides predicts the success of a colony more than the dosage of the poisons. Hives that are exposed to many different pesticides are more likely to experience queen deaths, devastating events for honeybee colonies. The researchers do note that some pesticide practices have changed since they last gathered data. They plan to investigate further and hope to come up with a plan that will reduce honeybees’ exposure to pesticides while still preserving important crops.


Kirsten S. Traynor et al. In-hive Pesticide Exposome: Assessing risks to migratory honey bees from in-hive pesticide contamination in the Eastern United States. Scientific Reports (2016).

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