title: Ant control efficacy of pyrethroids and fipronil on outdoor concrete surfaces.
abstract: BACKGROUND
  Urban and residential concrete surfaces are often treated with pesticides to control ants. Run-off from irrigation/rainfall can remove pesticides from concrete and contaminate urban waterways. Recent regulations and mitigations in regions such as California aim to reduce insecticide run-off (e.g. pyrethroids), but are often proposed without adequate consideration of their impact on ant control efficacy.
  
  
  METHODS
  We carried out an outdoor study with a side-by-side comparison between pesticide run-off potential and residual ant toxicity after exposing treated concrete to summer conditions and simulated precipitations.
  
  
  RESULTS
  Treatments with bifenthrin, permethrin or fipronil all showed fast ant knockdown initially, and over 50% of ants were killed within 16 h after 1-min contact with the treated surfaces. Shorter ant median lethal time (LT50) was observed on concrete treated with over-the-counter (OTC) granule/dust formulations than OTC liquid or professional formulations. However, the treated surfaces rapidly lost ant control efficacy after outdoor exposure and repeated precipitations. Except for OTC solid permethrin treatment, the ant toxicity disappeared after 20 days for all other formulation treatments. In contrast, pesticides were detected in run-off water from simulated precipitations even 89 days after the treatment, with levels above 0.5 µg L(-1) for bifenthrin, 30 µg L(-1) for permethrin and 0.15 µg L(-1) for fipronil. Pyrethroid run-offs from OTC solid formulations were >10 times higher than the other two formulations.
  
  
  CONCLUSIONS
  The results suggested viable options for run-off mitigation include decreasing use on concrete such as using crack/spot treatments instead of broadcast applications, limiting pesticide use on hardscapes away from water contact, and avoiding using dust/granule formulations on hardscapes.
authors.affiliation: Department of Environmental Sciences, University of California, Riverside, CA, 92521, USA; California Department of Pesticide Regulation, Sacramento, CA, 95812, USA.
authors.forename: Weiying
authors.initials: W
authors.lastname: Jiang
authors.forename: Andrew
authors.initials: A
authors.lastname: Soeprono
authors.forename: Michael K
authors.initials: MK
authors.lastname: Rust
authors.forename: Jay
authors.initials: J
authors.lastname: Gan
mesh_terms: D000818:Animals; D001000:Ants; D002626:Chemistry, Pharmaceutical; D007300:Insect Control; D007306:Insecticides / Q000737:chemistry*; D008962:Models, Theoretical; D011720:Pyrazoles / Q000737:chemistry*; D011722:Pyrethrins / Q000737:chemistry*; D011891:Rain / Q000737:chemistry; D012306:Risk; D012621:Seasons; D013499:Surface Properties; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D007306:Insecticides; D011720:Pyrazoles; D011722:Pyrethrins; D014874:Water Pollutants, Chemical; C082360:fipronil
keywords: ant control; bifenthrin; concrete; fipronil; hardscapes; permethrin