Biomass and Extracts of Metarhizium robertsii MT008 as Potential Biopesticides for Controlling the Fruit Fly Anastrepha obliqua

The fruit fly causes yield losses of 40 to 80% in various fruit crops, resulting in an approximate annual loss of USD 100 million in Colombia. Anastrepha obliqua is a significant pest for the mango production sector. Although biopesticides are promising alternatives for its control, there are currently no registered biopesticides derived from biomass or extracts of entomopathogenic fungi with the Colombian Agricultural Institute (ICA) for this purpose. This study demonstrates for the first time the potential of biomass and extracts from a native entomopathogenic fungus, Metarhizium robertsii MT008, cultivated through a liquid fermentation process, to effectively control both adult and preimaginal stages of A. obliqua. The optimal fermentation time was determined to be 5 days, producing the highest concentration of viable biomass (5.3 × 10⁵ CFU mL^-1), along with 75.89 ppm of destruxin A and 147.58 ppm of destruxin B. The fungal extract caused 100% mortality in A. obliqua adults within 48 h. While the biomass without formulation achieved 100% mortality, a biomass prototype achieved nearly 90% mortality at doses of 0.10 and 0.20 mg of dry biomass per gram of vermiculite against the preimaginal stages of the fruit fly by 24 days post-inoculation under laboratory conditions. The results demonstrate strong potential for advancing biopesticides, as combining these bioactive agents could allow more effective control of A. obliqua populations in field conditions by causing mortality at two different stages of its life cycle.