Endophytic Colonization by Beauveria bassiana and Metarhizium anisopliae in Maize Plants Affects the Fitness of Spodoptera frugiperda (Lepidoptera: Noctuidae)

The fall armyworm, Spodoptera frugiperda (Noctuidae; Lepidoptera), is a serious threat to food security as it has the potential to feed on over 353 plant species. To control this insect pest, endophytic colonization of entomopathogenic fungi (EPF) in plants is being considered as a safer and more effective alternative. This study evaluated the efficacy of two EPFs, Beauveria bassiana and Metarhizium anisopliae, for endophytic colonization using foliar spray and seed treatment methods on maize plants, and their impact on the survival, development, and fecundity of S. frugiperda. Both EPF effectively colonized the maize plants with foliar spray and seed treatment methods, resulting in 72-80% and 50-60% colonization rates, respectively, 14 days after inoculation. The EPF negatively impacted the development and fecundity of S. frugiperda. Larvae feeding on EPF-inoculated leaves had slower development (21.21 d for M. anisopliae and 20.64 d for B. bassiana) than the control treatment (20.27 d). The fecundity rate was also significantly reduced to 260.0-290.1 eggs/female with both EPF applications compared with the control treatment (435.6 eggs/female). Age-stage-specific parameters showed lower fecundity, life expectancy, and survival of S. frugiperda when they fed on both EPF-inoculated leaves compared with untreated leaves. Furthermore, both EPFs had a significant effect on population parameters such as intrinsic (r = 0.127 d^-1 for B. bassiana, and r = 0.125 d^-1 for M. anisopliae) and finite rate (λ = 1.135 d^-1 for B. bassiana, and λ = 1.1333 d^-1 for M. anisopliae) of S. frugiperda compared with the control (r = 0.133 d^-1 and λ = 1.146 d^-1). These findings suggest that EPF can be effectively used for the endophytic colonization of maize plants to control S. frugiperda. Therefore, these EPFs should be integrated into pest management programs for this pest.