Pesticide exposure for honey bees near agricultural fields

A variety of stressors have been implicated as potential causes for the decline of populations of honey bees and other pollinators, including pesticides. Neonicotinoid insecticides have been found in previous analyses. The routes of exposure, however, have remained largely undefined. Scientists from the Department of Entomology, Purdue University, West Lafayette, Indiana, United States of America, and from the Department of Analytical Chemistry, The Connecticut Agricultural Experiment Station, New Haven, Connecticut, United States of America used LC/MS-MS to analyze samples of honey bees, pollen stored in the hive and several potential exposure routes associated with plantings of neonicotinoid treated maize.
 

Their results demonstrate that bees are exposed to these compounds and other agricultural pesticides in several ways throughout the foraging period. During spring, extremely high levels of clothianidin and thiamethoxam were found in planter exhaust material produced during the planting of treated maize seed. The scientists also found neonicotinoids in the soil of each field they sampled, including unplanted fields. Plants visited by foraging bees growing near these fields were found to contain neonicotinoids as well, according to Plos One. This indicates deposition of neonicotinoids on the flowers, uptake by the root system, or both.

Dead bees collected near hive entrances during the spring sampling period were found to contain clothianidin as well. The scientists also detected the insecticide clothianidin in pollen collected by bees and stored in the hive. When maize plants in the field reached anthesis, maize pollen from treated seed was found to contain clothianidin and other pesticides; and honey bees in their study readily collected maize pollen. These findings clarify some of the mechanisms by which honey bees may be exposed to agricultural pesticides throughout the growing season.

These results have implications for a wide range of large-scale annual cropping systems that utilize neonicotinoid seed treatments. The full article and further information is available here: Plos One