Eric Mader, Pollinator Outreach Coordinator, the Xerces Society for Invertebrate Conservation

Pesticide poisoning of bees usually occurs in one of three different ways:

  1. The absorption of toxic chemicals through the bee’s exoskeleton;
  2. From drinking contaminated nectar; or
  3. From eating contaminated pollen during the larval development stage.

Other less common forms of pesticide poisoning can also occur. Leafcutter bees for example can collect contaminated leaf pieces for nest construction. The pesticides covering the leaf are then slowly absorbed by the larvae during development.

Pesticide poisoning often results directly in death. In other cases, however, sub-lethal effects may be observed. Often the nervous system is impacted causing spasms, impaired movement or navigation, and paralysis. Mutations and developmental problems of larvae may also be observed.

While insecticides are the most common culprit in bee poisonings, other agricultural chemicals including various herbicides, fungicides, and plant growth regulators may also have negative effects. Reducing the damage of these chemicals on bees requires an overall reduction of use, control of spray drift, and selection of products with the lowest possible toxicity.