Beauveria bassiana Ingested As Endophyte in Corn Is Present in the Gut, but Lacked Infectivity Against Larval Fall Armyworm (Spodoptera frugiperda)

The entomopathogenic fungus Beauveria can establish in plants as endophyte. We examined some interactions between Beauveria cf. bassiana living as plant-harmless endophyte in corn, and fall armyworm, Spodoptera frugiperda, feeding on these plants. Fall armyworm is a corn pest and it is susceptible to Beauveria infections. Corn seeds were inoculated with an endophytic Beauveria strain. After one month, plants obtained from seeds were fed to 2nd- and 4th-instar fall armyworm larvae for four days. Plant tissue was also plated on selective medium to confirm the presence of Beauveria in plants fed to larvae. After feeding, larvae were dissected and the gut was plated on selective medium to confirm presence of live Beauveria cells in the gut. Additional exposed larvae were further reared to detect Beauveria infections. Beauveria was extensively recovered as endophyte in corn (65% and 4% of all fungal colonies from inoculated vs. control plants, respectively). Beauveria grew from the gut of 30% (2nd instar) and 62% (4th instar) larvae fed endophytic Beauveria in plants; 2% and 0% in controls respectively). All differences were significant (p<0.05%). However, no Beauveria infections were induced on live, reared larvae after feeding on endophytic Beauveria.  Examination of endophyte-insect interactions is warranted.