Control of Phthorimaea absoluta Meyrick through a translaminar endophytic strain of Metarhizium brunneum Petch with systemic effect

Abstract: The endophytic behavior of the Metarhizium brunneum Petch strain EAMa 01/58-
Su, an entomopathogenic ascomycete (EA), offers potential for developing diverse strategic,
preventive, and curative approaches to control Phthorimaea absoluta Meyrick (Lepidoptera:
Gelechiidae), a major pest of tomatoes and the focus of this research. To evaluate the preventive strategy, the strain EAMa 01/58-Su was applied to the two basal leaves of the plant before larval infestation. The infestation involved L2 larvae placed on untreated distant leaves at 2, 7, and 14 days post-inoculation. Larval development to the adult stage was subsequently monitored. The fungal treatment led to a 31.3 % mortality rate among larvae on distant leaves, suggesting systemic activity of unknown origin, potentially linked to the induction of systemic resistance in the plant triggered by the fungal application. Furthermore, a targeted curative strategy was employed for both eggs-L1 larvae (on the leaf surface) and L2 larvae. For eggs-L1 larvae, plants were exposed to adults for one day to allow oviposition. For L2 larvae, plants were infested for one day to ensure larval establishment in plant tissues before applying the fungal suspension. This curative treatment achieved a substantial reduction of 78-90 % in the preimaginal population. Evidence of infection in the cadavers further confirmed the translaminar activity of this strain, as verified by molecular techniques. These results underscore the importance of this fungus as a multifunctional agent for integration into the integrated management of P. absoluta in tomatoes, especially considering the expected coexistence of systemic and translaminar actions within a heterogeneous pest population and its positive effects on crop growth.