Pathogenicity of Beauveria bassiana and Metarhizium flavoviride (Deuteromycotina) to Schistocerca americana (Orthoptera: Acrididae)

Abstract

The entomopathogenic fungi Beauveria bassiana (Balsamo) Vuillemin and Metarhizium flavoviride Gams and Rozspal have been widely tested for the suppression of grasshoppers. However, with the exception of Melanoplus sanguinipes (F.), there has been little research on Nearctic species. We examined the potential of these 2 microbial agents for control of the American grasshopper, Schistocerca americana (Drury), and the migratory grasshopper, M. sanguinipes. M. flavoviride was much more virulent than B. bassiana to both grasshopper species. At the conidial dosage of 1.2 × 105, M. flavoviride produced 69.2 and 74.2% mean mortality 7 d after treatment in S. americana and M. sanguinipes, respectively. In contrast, B. bassiana produced 1.7 and 11.7% mean mortality 7 d after treatment in S. americana and M. sanguinipes, respectively. Treatment with M. flavoviride also caused a significant reduction in feeding beginning 48 h after treatment of 6th-instar S. americana. Furthermore, M. flavoviride-treated S. americana showed an average reduction of 36.6% mean cumulative consumption, 5-8 d after treatment, when compared with untreated grasshoppers.