Effect of different spores and metabolites of Beauveria bassiana on larvae of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

Tomato leaf miner, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae) is so challenging in tomato farming. Its control depends on use of synthetic pesticides rather than biological control methods. Currently, entomopathogenic organisms are main focus in controlling crucial agricultural pests. B. bassiana is an essential candidate in T. absoluta control. However, its spores are limited in terms of viability and lifespan. The current work expanded B. bassiana activity spectrum by testing conidia, blastospores, extracellular enzymes and secondary metabolites against T. absoluta. Mass rearing of T. absoluta was achieved by growing tomato plants and feeding them inside of climatic chambers. Culturing of B. bassiana was conducted on the PDA medium. Blastospores, extracellular enzymes and secondary metabolites were obtained by submerged culture methods. Conidiospores and blastospores were counted with Thoma hemocytometer and light microscope. Metabolites were obtained by ultrafiltration and centrifugations. Their supernatants were split into separate dilutes and mix formulations. All biopesticide formulations were applied by spraying on each of 4 larval stages of T. absoluta under CRBD type. Data pertaining to larval mortality were collected, evaluated with Abbott formula and Microsoft and analyzed with SPSS ver.22. Larval mean mortalities were separated with Tukey's HSD test (P≤0.05). Control sprays consisted of water and Tween-80 and caused almost zero mortality. Generally, all formulations were significantly effective against T. absoluta larvae. Blastospores showed high effectivity to older larval stages. The mixed formulations of extracellular enzymes are more toxic to T. absoluta larvae than separate formulations. B. bassiana M6-4 isolate is a potential candidate for sustainable control of T. absoluta.