Formulation and bio-efficacy of different isolates of Beauveria bassiana against adults and third nymphal instar of desert locust (Schistocerca gregaria Forskål)

• Published in: Biological control 2024-11, Vol.198, p.105642, Article 105642
• Main Authors: Mwikali, Pamela C, Mwamburi, Lizzy A., Peter Musinguzi, Simon
• Format: Article
• Language: English
• Subjects: Beauveria bassiana; Biological control; Biopesticide formulation; Carrier materials; Desert locust
• ISSN: 1049-9644
• DOI: 10.1016/j.biocontrol.2024.105642

•Climate change has induced episodic upsurge in desert locust (Schistocerca gregaria)•There is increased use of entomopathogenic fungi for control of many insect species.•Beauveria bassiana is used to control insects pests including the desert locust.•Less information is available on bioefficacy of formulation desert locust control.•The isolates and formulations B. Bassiana were effective against desert locusts. Recently, the Horn of Africa witnessed a swift increase in the incidence of desert locust (Schistocerca gregaria) invasion. During outbreaks, pesticides are applied through aerial or ground spraying to kill the insects, and/or to prevent their spread to new grounds. However, after decades of extensive use, many drawbacks such as contamination of the environment, toxicity to non-target organisms, harmful residues on food, pest resistance, and bioaccumulation in the food chains emerged. Entomopathogenic fungi offer viable alternatives to chemical pesticides against many insect invasions, but few studies have tested their bio-efficacy in desert locusts. Therefore, the current study aimed at isolating, formulating local isolates 231, 334, 333, 341, 349, 351, 339 of Beauveria bassiana, and testing their bio-efficacy against larval and adult desert locusts. The 21-day experiment was conducted under controlled conditions in a greenhouse. Soil samples were collected from two agroecological zones in Isiolo and Laikipia Counties in Kenya. B. bassiana was isolated from the soil samples using the Galleria bait method and cultivated in Sabouraud Dextrose Agar Yeast (SDAY). The isolates were identified based on molecular techniques (DNA and PCR amplification). The conidia of the isolates were screened and bioassays on 30 locusts was conducted for 14 days. The best isolates eliciting over 90 % mortality during screening were used for formulations using three carrier materials (liquid paraffin, Diatomaceous Earth, and whey) which were again tested against adult and 3rd nymphal instars of the locusts. The stability of the formulations was also tested after 1 and 2 months. All the tested isolates of B. bassiana significantly outperformed the control and thus pathogenic to the adults and 3rd nymphal instars of S. gregaria under laboratory conditions. They caused mortality ranging from 57.8–100 % after 14 days post-incubation. The isolates 341, 231, and, 334 elicited 50 % mortality responses at concentrations 1.1 × 105 conidia/ml, 2.5 × 105 conidia/ml and 1.7 × 106 co