title: Infection of the malaria mosquito, Anopheles gambiae, with two species of entomopathogenic fungi: effects of concentration, co-formulation, exposure time and persistence.
abstract: BACKGROUND
  Entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana isolates have been shown to infect and reduce the survival of mosquito vectors.
  
  
  METHODS
  Here four different bioassays were conducted to study the effect of conidia concentration, co-formulation, exposure time and persistence of the isolates M. anisopliae ICIPE-30 and B. bassiana I93-925 on infection and survival rates of female Anopheles gambiae sensu stricto. Test concentrations and exposure times ranged between 1 x 10(7) - 4 x 10(10) conidia m(-2) and 15 min - 6 h. In co-formulations, 2 x 10(10) conidia m(-2) of both fungus isolates were mixed at ratios of 4:1, 2:1, 1:1,1:0, 0:1, 1:2 and 1:4. To determine persistence, mosquitoes were exposed to surfaces treated 1, 14 or 28 d previously, with conidia concentrations of 2 x 10(9), 2 x 10(10) or 4 x 10(10).
  
  
  RESULTS
  Mosquito survival varied with conidia concentration; 2 x 10(10) conidia m(-2) was the concentration above which no further reductions in survival were detectable for both isolates of fungus. The survival of mosquitoes exposed to single and co-formulated treatments was similar and no synergistic or additive effects were observed. Mosquitoes were infected within 30 min and longer exposure times did not result in a more rapid killing effect. Fifteen min exposure still achieved considerable mortality rates (100% mortality by 14 d) of mosquitoes, but at lower speed than with 30 min exposure (100% mortality by 9 d). Conidia remained infective up to 28 d post-application but higher concentrations did not increase persistence.
  
  
  CONCLUSIONS
  Both fungus isolates are effective and persistent at low concentrations and short exposure times.
authors.affiliation: Biomedical and Environmental Group, Ifakara Health Institute, PO Box 53, Off Mlabani Passage, Ifakara, Tanzania. llaurent@ihi.or.tz
authors.forename: Ladslaus L
authors.initials: LL
authors.lastname: Mnyone
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Kirby
authors.forename: Dickson W
authors.initials: DW
authors.lastname: Lwetoijera
authors.forename: Monica W
authors.initials: MW
authors.lastname: Mpingwa
authors.forename: Bart G J
authors.initials: BG
authors.lastname: Knols
authors.forename: Willem
authors.initials: W
authors.lastname: Takken
authors.forename: Tanya L
authors.initials: TL
authors.lastname: Russell
mesh_terms: D000818:Animals; D000852:Anopheles / Q000382:microbiology*; D052982:Beauveria / Q000254:growth & development*; D005260:Female; D052981:Metarhizium / Q000254:growth & development*; D009032:Mosquito Control / Q000379:methods; D013997:Time Factors