Submitted to: Entomological Society of America Annual Meeting North Central Branch
Publication Type: Abstract Only
Publication Acceptance Date: 3/18/2001
Publication Date: N/A
Technical Abstract: Isolates of the entomopathogenic fungus, Metarhizium anisopliae (Metschnikoff) Sorokin have exhibited high levels of virulence to larvae of important dipteran insect pests, including the tsetse fly and the house fly. Also, preliminary investigations have demonstrated infectivity of M. anisopliae with all stages of our target insect, the sugarbeet root maggot (SBRM), Tetanops myopaeformis Roder. However, actual Lethal dose (LD50) and lethal time (LT50) values have not been established. Therefore, our investigation was carried out to determine these values using time-dosage mortality analysis and thereby, estimate the virulence of M. anisopliae to SBRM larvae. Fungi were cultured and a mixture of conidia and hyphae were obtained from the culture. Suspensions were adjusted to achieve concentrations of 1 x 10**8 conidia per ml of solution (1% polyoxyethylene-sorbitan monooleate), and the following serial dilution treatments were established for bioassays: 1 x 10**8, 1 x 10**7, 1 x 10**6, 1 x 10**5, 1 x 10**4, and 1 x 10**3 per ml. Additional treatments included 1% polyoxyethylene-sorbitan monooleate and water controls. The experiment was arranged in a completely randomized design with eight replications. Treatment applications consisted of dipping larvae (10 per treatment) in solution and placing them in a petri dish for mortality assessments. Larval mortality was assessed every 24 h. Cadavers were removed at each assessment and placed individually in petri dishes containing Potato Dextrose Agar to determine if mortality was due to mycosis. Surviving larvae were allowed to pupate and emerge as adults. Results of these bioassays and associated assessments of pupation will be presented.