title: Sublethal Effects of Imidacloprid on Honey Bee Colony Growth and Activity at Three Sites in the U.S.
abstract: Imidacloprid is a neonicotinoid pesticide heavily used by the agricultural industry and shown to have negative impacts on honey bees above certain concentrations. We evaluated the effects of different imidacloprid concentrations in sugar syrup using cage and field studies, and across different environments. Honey bee colonies fed sublethal concentrations of imidicloprid (0, 5, 20 and 100 ppb) over 6 weeks in field trials at a desert site (Arizona), a site near intensive agriculture (Arkansas) and a site with little nearby agriculture but abundant natural forage (Mississippi) were monitored with respect to colony metrics, such as adult bee and brood population sizes, as well as pesticide residues. Hive weight and internal hive temperature were monitored continuously over two trials in Arizona. Colonies fed 100 ppb imidacloprid in Arizona had significantly lower adult bee populations, brood surface areas and average frame weights, and reduced temperature control, compared to colonies in one or more of the other treatment groups, and consumption rates of those colonies were lower compared to other colonies in Arizona and Arkansas, although no differences in capped brood or average frame weight were observed among treatments in Arkansas. At the Mississippi site, also rich in alternative forage, colonies fed 5 ppb imidacloprid had less capped brood than control colonies, but contamination of control colonies was detected. In contrast, significantly higher daily hive weight variability among colonies fed 5 ppb imidacloprid in Arizona suggested greater foraging activity during a nectar flow post treatment, than any other treatment group. Imidacloprid concentrations in stored honey corresponded well with the respective syrup concentrations fed to the colonies and remained stable within the hive for at least 7 months after the end of treatment.
authors.affiliation: Carl Hayden Bee Research Center, USDA-ARS, Tucson, AZ United States of America.
authors.forename: William G
authors.identifier: http://orcid.org/0000-0002-1759-6950
authors.initials: WG
authors.lastname: Meikle
authors.affiliation: Southern Horticultural Laboratory, USDA-ARS, Poplarville, MS United States of America.
authors.forename: John J
authors.initials: JJ
authors.lastname: Adamczyk
authors.affiliation: Carl Hayden Bee Research Center, USDA-ARS, Tucson, AZ United States of America.
authors.forename: Milagra
authors.initials: M
authors.lastname: Weiss
authors.affiliation: Mississippi State University, South MS Branch Experiment Station, Poplarville, MS United States of America.
authors.forename: Ales
authors.initials: A
authors.lastname: Gregorc
authors.affiliation: University of Arkansas Division of Agriculture Cooperative Extension Service, Lonoke Res. & Ext. Ctr., Lonoke, AR United States of America.
authors.forename: Don R
authors.initials: DR
authors.lastname: Johnson
authors.affiliation: The University of Tennessee, West Tennessee Research & Education Center, 605 Airways Blvd, Jackson, TN United States of America.
authors.forename: Scott D
authors.initials: SD
authors.lastname: Stewart
authors.affiliation: University of Arkansas Division of Agriculture Cooperative Extension Service, 2301 South University, Little Rock, AR United States of America.
authors.forename: Jon
authors.initials: J
authors.lastname: Zawislak
authors.affiliation: Carl Hayden Bee Research Center, USDA-ARS, Tucson, AZ United States of America.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Carroll
authors.affiliation: University of Arkansas Division of Agriculture Cooperative Extension Service, Lonoke Res. & Ext. Ctr., Lonoke, AR United States of America.
authors.forename: Gus M
authors.initials: GM
authors.lastname: Lorenz
mesh_terms: D000818:Animals; D001516:Bees / Q000187:drug effects* / Q000254:growth & development* / Q000378:metabolism; D007093:Imidazoles / Q000009:adverse effects*; D007306:Insecticides / Q000009:adverse effects*; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000009:adverse effects*; D010575:Pesticides / Q000009:adverse effects; D014481:United States
chemical_list: D007093:Imidazoles; D007306:Insecticides; D000073943:Neonicotinoids; D009574:Nitro Compounds; D010575:Pesticides; C082359:imidacloprid