Efficacy of commercial and non-commercial strains of entomopathogenic fungi against the peach aphid Myzus persicae (Sulz.)

Abstract: The efficacy of twenty-two strains of entomopatogenic fungi, isolated from natural outbreaks and also from commercial products (Lecanicillium (Verticillium) lecanii (Zimm.) Zare & Gams, Lecanicillium longisporum (Petch) Zare & W. Gams, Beauveria bassiana (Bals.-Criv.) Vuill, Metarhizium brunneum (anisopliae) (Metschn.) Sorokin, Isaria fumosorosea Wize, Paecilomyces lilacinus (Thom) Samson, Hirsutella kirchneri (O. Rostr.) Minter, B. L. Brady & R. A. Hall and Hirsutella thompsonii F. E. Fisher), was tested for the control of the peach aphid Myzus persicae (Sulz.). Pathogenicity of the selected isolates was first evaluated through a quick screening test: aphids were exposed to conidia for 5 minutes, by gently transferring them to sporulated cultures (on PDA), and then transferred to plastic boxes (detached leaf bioassay) and kept at 20 °C, 80% RH for 10 days. Signs of infections were assessed daily. The most virulent strains were selected for the next step, the laboratory trial. For effectiveness of strains in the laboratory trial, conidiospores in three different doses (105, 107, 109 conidia/ml) were sprayed on aphids. Treated aphids were kept to detached leaves of sweet pepper on 1% water agar for pathogen incubation and pathogenicity of most fungal species was confirmed at all the three doses. The most virulent strains were tested in greenhouse, on aphids reared on potted plants. All the tested strains gave significant control of aphid in the laboratory trial, but only Lecanicillium longisporum (Vertalec® isolate) showed a reasonable control of aphids in greenhouse trial with infection rates up to 40%. An increasing trend in mortality of aphids (epizootic) was observed in all the treatments with an increase in aphid population.