Sublethal Effects of the Insecticide Pyrifluquinazon on the European Honey Bee (Hymenoptera: Apidae)

Pyrifluquinazon (PQZ) is an Insecticide Resistance Action Committee (IRAC) Group 9 insecticide that has recently been registered for use in the United States for control of soft-bodied sucking insect pests. Although it has been classified as practically nontoxic to honey bees, Apis mellifera L. (Hymenoptera: Apidae), based on acute contact bioassays, additional information on sublethal effects of this insecticide on honey bees is lacking. Using a combination of laboratory assays with video movement tracking software and near-field evaluations of colonies foraging in a high-tunnel experiment, we determined that, when fed PQZ at a concentration of 84 mg active ingredient (ai)/liter (= ppm) in sugar water, a reduction in overall movement by the foraging worker bees was observed. However, when provided with honey reserves in the hive, honey bees rejected the PQZ-treated sugar water. These results indicate that, if ingested at levels of 84 mg ai/liter, PQZ could have a negative effect on honey bee behavior; however, honey bee workers appear to be able to detect the presence of PQZ in their food and reject it.