Harnessing indigenous entomopathogenic fungi for biopesticide development against Tuta absoluta in Tanzania

Abstract

The invasive pest Tuta absoluta (Meyrick) poses a significant risk to global tomato crops, particularly affecting Tanzania's food security and economy. Currently, control strategies for this pest rely on synthetic pesticides, which are ineffective and pose a great environmental threat to the ecosystem. This underscores the urgent need for search of ecofriendly alternative to combat this invasive pest. The agar plate method was employed for isolation and purification of fungi from the soil. From soil samples collected in Arusha's tomato fields, 36 fungal isolates were discovered, and subjected to rigorous morphological and biochemical characterization. Of these, 8 demonstrating enzyme activity capable of breaking down insect cuticles, indicating their potential as insecticides. These isolates were subjected molecular characterizations, including DNA sequencing and analyses using the BLAST program available at the National Center for Biological Information (NCBI), to ascertain their identity. The isolates showed 100 % similarity with Aspergillus terreus, Penicillium steckii, Purpureocillium lilacinum, Aspergillus flavus and Aspergillus versicolor of GeneBank accession numbers MN463005.1, MK179265.1, MN242828.1, MN559660.1 and MH270605.1, respectively. Bioassays conducted on T. absoluta larvae with spore suspensions of these fungi revealed significant larval mortality rates for A. terreus, P. steckii, and two strains of P. lilacinum, with Penicillium steckii achieving up to 100 % mortality at a concentration of 10⁷ spores/mL. The study findings highlight the potential of using native fungi, particularly Aspergillus terreus, Penicillium steckii, and Purpureocillium lilacinum, as effective biopesticides against T. absoluta, underscoring the importance of harnessing indigenous microbial resources for sustainable agricultural pest control and food security.