Selection of promising fungal biological control agent of the western flower thrips Frankliniella occidentalis (Pergande)

Aims: Larval stages of Frankliniella occidentalis are known to be refractory to fungal infection compared with the adult stage. The objective of this study was to identify promising fungal isolate(s) for the control of larval stages of F.similar to occidentalis. Methods and Results: Ten isolates of Metarhizium anisopliae and eight of Beauveria bassiana were screened for virulence against second-instar larvae of F.similar to occidentalis. Conidial production and genetic polymorphism were also investigated. Metarhizium anisopliae isolates ICIPE 7, ICIPE 20, ICIPE 69 and ICIPE 665 had the shortest LT50 values of 8.08.9 days. ICIPE 69, ICIPE 7 and ICIPE 20 had the lowest LC50 values of 1.1 x 107, 2.0 x 107 and 3.0 x 107 conidia ml-1, respectively. Metarhizium anisopliae isolate ICIPE 69 produced significantly more conidia than M.similar to anisopliae isolates ICIPE 7 and ICIPE 20. Internally transcribed spacers sequences alignment showed differences in nucleotides composition, which can partly explain differences in virulence. Conclusion: These results coupled with the previous ones on virulence and field efficacy against other species of thrips make M.similar to anisopliae isolate ICIPE 69 a good candidate. Significance and Impact of the Study: Metarhizium anisopliae isolate ICIPE 69 can be suggested for development as fungus-based biopesticide for thrips management.