ARS | Publication request: Efficacy of Metarhizium anisopliae microsclerotial granules

Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 31, 2008
Publication Date: October 1, 2008
Repository URL: http://hdl.handle.net/10113/22869
Citation: Jaronski, S., Jackson, M.A. 2008. Efficacy of Metarhizium anisopliae microsclerotial granules. Biocontrol Science and Technology. 18(8):849-863.

Interpretive Summary: The entomopathogenic fungus Metarhizium anisopliae has very recently been shown to produce microsclerotia ' compact, heavily melanized, hyphal aggregates ' in liquid media. These microsclerotia, in turn, can be made into shelf-stable granular formulations for use against soil dwelling insect pasts. This paper reports to successful outcome of soil incorporation bioassays evaluating microsclerotia-containing granules against larvae of the sugarbeet root maggot, Tetanops myopaeformis, a major, root attacking pest of sugar beets. Microsclerotia-containing granules of three fungal isolates produced in high carbo, high carbon:nitrogen ratio media were superior to mycelium-containing granules and also to other more typical granules made of conidia bound to a nutritive granular carrier (corn grits).

Technical Abstract: Soil incorporation bioassays of dried microsclerotial (MS) preparations of three isolates of M. anisopliae isolates were conducted using third instar Tetanops myopaeformis (sugarbeet root maggot) in clay and/or clay loam field soils as a model system to demonstrate efficacy. At rates as low as 23 mg MS granules/100g dry soil, the biocontrol efficacy of MS granules of M. anisopliae Strain F52 produced in liquid media with a high carbon concentration (36 g/L) and high C:N ratios (30:1, 50:1) were superior to MS preparations produced in low carbon (8g carbon/L) media and a high carbon medium with a 10:1 C:N ratio. Bioassays using MS formulations of M. anisopliae strains MA1200 and TM109 produced in high carbon and high C:N ratio media were superior in efficacy to the other MS production media tested. MS preparations of M. anisopliae F52 showed superior efficacy against the sugarbeet root maggot in comparison with more conventional, conidia-covered nutritive (corn grit) granules in a clay and clay soil. The MS granules were also highly efficacious against the sugarbeet root maggot at soil moisture levels as low as 0.983 Aw (-2.33 MPa). Granular preparations incorporating Metarhizium MS can serve as a viable formulation for the use of this fungus against soil insects.