Submitted to: Advances in Applied Acridology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/1/2005
Publication Date: 7/1/2008
Citation: Jaronski, S. 2008. Australian metarhizium anisopliae var. acridum strain fi985 vs. beauveria bassiana strain gha - laboratory efficacy against north american acridids and anabrus simplex. Advances in Applied Acridology. Interpretive Summary: An isolate of the fungus Metarhizium that is being commercialized for locust control in Australia was evaluated in the laboratory against eleven North American grasshopper species and the Mormon Cricket. The fungus was compared to another insect pathogenic fungus, Beauveria bassiana Strain GHA, which has been commercialized in the U.S. for a variety of insect including grasshoppers. The Australian fungus was considerably more pathogenic for all the tested grasshoppers by several orders of magnitude. A dose sufficient to kill 50% of exposed grasshoppers ('LD50') was 2700-5600 spores per insect (depending on the species)for the Metarhizium, while the LD50 for Beauveria ranged from 271,00 to 2,840,000 spores/insect. Of considerable interest was that immature Mormon Crickets were 3.4 times more susceptible to the Metarhizium than to the Beauveria. Adult Mormon Crickets were 8.5 times more susceptible. Laboratory tests simulating Low Volume aerial application of spores to grasshoppers indicated that efficacious field rates of the Metarhizium could be 25-50% of those for the Beauveria.
Technical Abstract: Metarhizium anisopliae var. acridum Strain FI985 is being developed as a mycoinsecticide against locusts in Australia. It may a commercially viable microbial tool for managing grasshoppers in the U.S. Basic information is needed about the susceptibility of North America Orthoptera to the fungus. Susceptibility of adult Melanoplus sanguinipes, M. differentialis, M. bivitattus, M. packardi, M. femurrubrum, M. dawsoni, Phoetaliodes nebracensis, Ageneotettix deorum, Aulocara elliotti, Eritettix costalis, Schistocerca americana, and Anabrus simplex to FI985, and to Beauveria bassiana Strain GHA, commercialized in the U.S. for the control of Orthoptera and other insects, was assessed lettuce disk assays, direct topical application and simulated low volume aerial sprays. Based on mean LD50 in lettuce disk assays, S. americana was 66.5'fold more susceptible to FI985 than to GHA. Similarly, M. sanguinipes was 278-fold more susceptible to FI985. LD50 ratios for FI985/GHA for other grasshopper species ranged from 41.3 (M. bivitattus) to 709.5 (M. differentialis). LD50s for FI985 ranged from 2755 to 5569 spores per insect; GHA LD50 values ranged from 2.7E5 to 2.8E6 spores/insect. Mormon Cricket nymphs were more susceptible to FI985 in direct topical application assays, (Relative Potency of 3.4); with adults FI985 had a mean Relative Potency of 8.5. LD50s of the FI985 were 3.4E4 spores/insect for the nymphs and 4.1E4 spores/insect for the adults. At 2.5E13 conidia/ha in a simulated low volume aerial spray, FI985 was significantly more efficacious than Beauveria GHA for all the Melanoplus species, and P. nebracensis, exceeding 80% fungus-induced mortality, but not A. deorum and E. costalis. Efficacy of FI985 at 1.25E13/ha with most of the tested species was greater than GHA, at 2.5E13 spores/ha.