Effects of symbiotic bacteria on the parasitism efficacy of Aphidius gifuensis against Myzus persicae.

Aphidius gifuensis is an important parasitic wasp used to control Myzus persicae (tobacco aphid), a key pest in tobacco-producing areas. Over the past 10 years, the use of A. gifuensis has been widely promoted, and its natural population has steadily increased, playing a crucial role in aphid control and the prevention of aphid-transmitted viral diseases. However, long-term aphid protection and inbreeding of A. gifuensis populations have led to the degeneration of the species, reduced parasitism efficiency, and increased control costs. In response to these challenges, this study investigated the effects of symbiotic bacteria on the parasitism and reproductive capacity of A. gifuensis. The results show that Bacillus subtilis and Exiguobacterium gifuensis significantly promoted the parasitism rate of A. gifuensis, with the highest increases of 5.33 and 3.67%, respectively, compared to the control. Additionally, the presence of Acinetobacter radioresistens altered the activity of the superoxide dismutase (SOD) enzyme in A. gifuensis. At all tested concentrations, except for 0.97 × 1010 CFU/mL-1, SOD enzyme protein levels were inhibited, with the greatest reduction of 1.81% compared to the control. Furthermore, A. radioresistens significantly reduced the total activity of the SOD enzyme by 1.54%. Bacillus subtilis also significantly suppressed phenoloxidase activity, which was reduced by 44.78% compared to the control. These findings suggest that B. subtilis and E. gifuensis are beneficial for enhancing the parasitism efficacy of A. gifuensis in controlling M. persicae.