Entomopathogenic potential of Bacillus subtilis and Bacillus amyloliquefaciens strains against Musca domestica under controlled conditions

Abstract

The housefly, Musca domestica L. (Diptera: Muscidae), is a key pest in animal production areas; the resistance of this insect to chemical insecticides makes it necessary to develop new control alternatives. The aim of this work was to study the entomopathogenic activity of eight strains of Bacillus subtilis Ehrenberg ssp. subtilis and two strains of Bacillus amyloliquefaciens Priest et al., isolated from different ecological niches, against the housefly. Cell suspension (CS) of each Bacillus strain and cell-free supernatant (CFS) and crude lipopeptide fraction (LF) of 7 mg ml−1 of B. amyloliquefaciens CBMDDrag3 and CBMDLO3 strains were evaluated. Various housefly cohorts, resulting from systematic crosses, were used for the bioassays. The eight strains of B. subtilis ssp. subtilis affected the survival of the larvae by 10–20%, whereas strains CBMDDrag3 and CBMDLO3 decreased the survival of these individuals by 30 and 50%, respectively. CBMDLO3 was the strain with the highest pupicidal activity, reducing the survival of these individuals by up to 50%. To evaluate the effect of CBMDLO3 on the fertility of housefly females and longevity of individuals, adults from larvae fed CS, CFS, and LF were used. Females from the CS and CFS diets reduced their oviposition capacity by approximately 50% compared to females from the DL and DMH control diets (i.e., DCS 144.3 eggs, DCFS 128 eggs, and DL 346.5 eggs, respectively). On the other hand, the life cycle of females and males was only affected by LF, i.e., 4 and 6 days shorter than the control, respectively. The UV MALDI TOF analysis of CBMDLO3 LF identified several surfactin homologues. Results show the ability of B. amyloliquefaciens CBMDLO3 strain to reduce the survival of larvae and pupae of M. domestica and the fecundity of female adults, thus allowing cycles of inhibition of housefly development in laying hen farms. Therefore, B. amyloliquefaciens CBMDLO3 strain can make an important contribution to the continuous search of new biocontrol alternatives.