PATHOGENICITY OF BEAUVERIA-BASSIANA AND METARHIZIUM-FLAVOVIRIDE (DEUTEROMYCOTINA) TO SCHISTOCERCA-AMERICANA (ORTHOPTERA, ACRIDIDAE)

The entomopathogenic fungi Beauveria bassiana (Balsamo) Vuillemin and Metarhizium flavoviride Gams and Rozspal have been widely tested for t he suppression of grasshoppers. However, with the exception of Melanop lus sanguinipes (F.), there has been little research on Nearctic speci es. We examined the potential of these 2 microbial agents for control of the American grasshopper, Schistocerca americana (Drury), and the m igratory grasshopper, M. sanguinipes. M. flavoviride was much more vir ulent than B. bassiana to both grasshopper species. At the conidial do sage of 1.2 x 10(5), M, flavoviride produced 69.2 and 74.2% mean morta lity 7 d after treatment in S. americana and il. sanguinipes, respecti vely. In contrast, B, bassiana produced 1.7 and 11.7% mean mortality 7 d after treatment in S. americana and M. sanguinipes, respectively. T reatment with M. flavoviride also caused a significant reduction in fe eding beginning 48 h after treatment of Gth-instar S. americana. Furth ermore, M, flavoviride-treated S. americana showed an average reductio n of 36.6% mean cumulative consumption, 5-8 d after treatment, when co mpared with untreated grasshoppers.