title: Different toxic and hormetic responses of Bombus impatiens to Beauveria bassiana, Bacillus subtilis and spirotetramat.
abstract: BACKGROUND
  Pollinator exposure to pesticides is a concern in agricultural systems that depend on pollinators for crop production. However, not all pesticides elicit toxic effects, and response to a pesticide will vary depending on dose and exposure route. The effects of biopesticide formulations of Bacillus subtilis and Beauveria bassiana and of the tetramic acid insecticide spirotetramat on the common eastern bumblebee, Bombus impatiens, were evaluated. Microcolonies of bees were exposed to field-rate or lower concentrations, and data were collected over 60 days.
  
  
  RESULTS
  When ingested, field rates of spirotetramat caused high mortality after 10 days, and B. subtilis significantly reduced drone production, number of days to oviposition and number of days to drone emergence. Converse to effects observed following ingestion, topical applications of B. subtilis at concentrations less than the recommended field rate resulted in a hormetic response, with significantly increased drone production. Topical application of spirotetramat and oral or topical application of B. bassiana had no effects on bees.
  
  
  CONCLUSIONS
  Spirotetramat and B. subtilis can induce adverse effects on B. impatiens, but hormetic effects following B. subtilis treatment can also occur, depending on exposure route. Additional experiments are required to determine whether similar toxic or hormetic effects occur under more realistic field conditions.
authors.affiliation: Department of Environmental Sciences, Faculty of Agriculture, Dalhousie University, Truro, NS, Canada.
authors.forename: Krilen
authors.initials: K
authors.lastname: Ramanaidu
authors.forename: G Christopher
authors.initials: GC
authors.lastname: Cutler
mesh_terms: D000818:Animals; D001372:Aza Compounds / Q000633:toxicity*; D001412:Bacillus subtilis / Q000502:physiology*; D052982:Beauveria / Q000502:physiology*; D001516:Bees / Q000187:drug effects* / Q000382:microbiology* / Q000502:physiology; D059165:Hormesis / Q000187:drug effects; D007306:Insecticides / Q000633:toxicity*; D012098:Reproduction / Q000187:drug effects; D013141:Spiro Compounds / Q000633:toxicity*
chemical_list: D001372:Aza Compounds; D007306:Insecticides; D013141:Spiro Compounds; C570705:spirotetramat
keywords: Bacillus subtilis; Beauveria bassiana; Bombus impatiens; hormesis; spirotetramat; sublethal response