Isolation and characterization of five Purpureocillium strains from Algerian soils and assessment of their larvicidal activity against Culex pipiens (Diptera, Culicidae)

Abstract

In Algeria, Culex pipiens is the most important mosquito species due to its wide geographical distribution, abundance and nuisance. This specie transmits multiple arboviruses such as the West Nile virus and encephalitis virus that have a global impact on human health. Multiple strategies are adopted for its control including elimination of mosquito breeding sites, by improving water storage and solid waste disposal, as well as treating breeding sites with biological or chemical larvicidal components. This study reports the isolation, morphological and molecular characterization as well as virulence of five entomopathogenic fungi strains, from Algerian soils, against 3rd instar larvae of Cx. pipiens. Based on morphology and ITS sequences, all fungal strains were assigned to genus Purpureocillium including three P. lavendulum strains (RS10B, RS7 and RS5 under the GenBank accession numbers MW426500, MW426502 and MW426503, respectively) and two P. lilacinum strains (RS10A and MICH1 under the GenBank accession numbers MW426501 and OL614981, respectively). These two species were reported for the first time in Algeria and until now, no study have reported the virulence of P. lavendulum against Cx. pipiens. Furthermore, the strains were tested for their efficacy against 3rd instar larvae of Cx. pipiens at 1 × 106, 1 × 107 and 1 × 108 conidia/mL concentration under laboratory conditions. Among these strains, RS10A and RS10B were the most effective strains due to their relatively low LC50, LT50 and LT90 values. These results indicated that these two entomopathogenic fungi strains have potential as biocontrol agents of Cx. pipiens.