Isolation, fermentation, and formulation of entomopathogenic fungi virulent against adults of Diaphorina citri

• Published in: Pest management science 2021-09, Vol.77 (9), p.4040-4053
• Main Authors: Awan, Umar Anwar, Meng, Lixue, Xia, Shuang, Raza, Muhammad Fahim, Zhang, Zhenyu, Zhang, Hongyu
• Format: Article
• Language: English
• Subjects: Adults; Asian citrus psyllid (Diaphorina citri); Beauveria bassiana; Biological control; Citrus fruits; Conidia; Cordyceps javanica; Diaphorina citri; Entomopathogenic fungi; Environmental effects; Fermentation; Flour; Fusarium fujikuroi; light/dark cycle; Morphology; oil‐based formulation; Phylogeny; Sesame oil; Shelf life; solid‐state fermentation; soybean meal; Soybeans; Substrates; Virulence
• ISSN: 1526-498X; 1526-4998
• DOI: 10.1002/ps.6429

BACKGROUND Mycopesticides are important for integrated management of the Asian citrus psyllid, Diaphorina citri. However, there are few reports on the fermentation and formulation for mycopesticides with high virulence against D. citri. RESULTS From four different locations in South China, 12 fungal strains were isolated and classified into Beauveria bassiana (two isolates), Fusarium fujikuroi (five isolates), and Cordyceps javanica (five isolates) based on the phylogenetic analysis of ITS1‐5.8S rDNA‐ITS4 and morphology of colonies and conidia. Based on the highest initial virulence (86.52 ± 2.35%) and best growth characteristics, F‐HY002‐ACPHali was further optimized for biphasic fermentation (7.85 ± 2.62 × 109 g–1 dry substrate) with soybean meal + cottonseed flour (1:1) as the solid substrate and full light as the light/dark cycle. Furthermore, the oil‐based conidial formulation was optimized with sesame oil as an effective carrier, which significantly enhanced conidial shelf life up to 16 weeks at 26 °C and 4 °C, thermo‐stress (50 °C) and UV‐B stress resistance, and virulence against adults of D. citri with increased mortalities and decreased LT50 in comparison to that of unformulated conidia. CONCLUSION Our results not only provide a valuable native strain with high virulence against adults of D. citri, but also imply the soybean meal + cottonseed flour as valuable solid substrate, full‐light exposure as environmental stimuli for solid‐state fermentation, and the sesame oil as an effective carrier for the formulation of the C. javanica. These findings will facilitate the development of a potential mycopesticide for the biological control of Asian citrus psyllid. By optimizing the biphasic fermentation and formulation of Cordyceps javanica F‐HY002‐ACPHali with good nutritional and environmental conditions, we developed a potential mycopesticide for the biocontrol of Diaphorina citri. ​ © 2021 Society of Chemical Industry.