Strain FI985 Metarhizium anisopliae var. acridum, under development as a locust biocontrol agent in Australia, was bioassayed against a series of melanopline, gomphocerine, and oedipodine grasshoppers, and the Mormon Cricket, Anabrus simplex, a tettigonid. One or more different application methods were used: a lettuce disk assay, direct topical application, and a simulated ULV spray exposure. Beauveria bassiana Strain GHA, registered for use in the U.S. for grasshopper control, was used as a comparative standard in all bioassays. The following orthopteran species were bioassayed: Melanoplus sanguinipes (both wild and from a non-diapausing colony), M. bivitattus, M. differentialis, M. infantilis, M. packardii, M. dawsoni, M. femurrubrum, Phoetaloides nebracensis, Ageneotettix deorum, Aulocara elliotti, Encoptolophus costalis, Camnula pellucida, and Schistocerca americana (from a lab colony). The tested insects were either field collected adults or offspring derived from field-collected females and reared to adulthood. In a few cases late nymphal instars were also bioassayed.

FI985 was observed to be highly infectious and virulent for the all the acridids tested, and, except for Anabrus adults, was much more efficacious than the Beauveria. The 7-day LD50 for FI985 was generally less than 3000 conidia per insect for most species. Interestingly, the colonized, non-diapause M. sanguinipes and wild counterparts were equally susceptible to both fungi, in contrast to previous observations.