Evaluation of indigenous isolates of Beuveria bassiana (Balsamo) Vuillemin (Deuteromycotina: Hyphomycetes) against the cotton aphid Aphis gossypii Glover

The cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is one of the most important pests and causes major damage to cultivated plants in Turkey. It has recently become a serious problem in Antalya (southwestern Turkey) due to its high resistance to insecticides used. To address this problem, the present study aimed to evaluate the pathogenicity of five indigenous Beuveria bassiana (Balsamo) Vuillemin (Deuteromycotina: Hyphomycetes) isolates (BbFn-2, BbKm-2, BbSr-2, BbDs-4, and BbDm-2) with high virulence in previous studies against the pest. All the isolates were tested at five different conidial concentrations (1 × 10⁵, 1 × 10⁶, 1 × 10⁷, 1 × 10⁸ and 1 × 10⁹ conidia mL⁻¹) against the nymphs and adults of A. gossypii using Petri dish and pot trials in the laboratory. The results from the bioassays showed that virulence of the isolates increased significantly with elapsed time up to 10 days after inoculation. All five B. bassiana isolates at the highest concentration (1 × 10⁹ conidia mL⁻¹) caused mortalities ranged from 83.3% to 100% in both nymphs and adults 10 days post-treatment. While the LT₅₀ and LT₉₅ values of the isolates were 1.72–2.12 days and 4.81–8.49 days, respectively, for the nymphs, they were calculated for the adults as 1.65–2.54 days and 4.66–12.93 days, respectively. Results of the phylogenetic analysis showed that these five B. bassiana isolates had high similarities (ranging from 99 to 100%) with the other B. bassiana isolates in GenBank. All the results suggest that above-mentioned five indigenous B. bassiana isolates have significant biocontrol potential against A. gossypii.