ABSTRACT
The effect of Metarhizium anisopliae (Metsch.) Sorokin on Astyanax scabripinnis (Jenyns, 1842) (Pisces, Characidae) under laboratory conditions was evaluated. Aqueous conidial suspensions either with a minimum viability of 90% or containing conidia rendered unviable by autoclaving were applied in fish tanks containing A. scabripinnis, at the concentration of 6.5 × 1010 conidia/fish tank (equivalent to 5 × 1015 conidia/ha, which represents 1000 times the recommended concentration for the control of pasture spittlebugs, the main target pest of this entomopathogen in Brazil). Water and fish samples were analyzed; the fish gills and stomachs were dissected at different time intervals to evaluate the presence of conidia. Fish behavior and mortality were observed daily in both treatments. The morphology of gill and liver cells was evaluated in the surviving fish. No changes in the number of conidia were verified in the gills throughout 16 days of contact; in the stomach, there was a slight initial increase followed by a steady reduction. Conidial viability decreased in all places evaluated 24 hours after application. No fish death or any behavioral alterations occurred after 30 days of contact, indicating the absence of adverse effects associated with the entomopathogen on the test organisms. The absence of signs of infectivity and other adverse effects are a further indication in favor of the use of M. anisopliae as a biopesticide.
KEY WORDS
Nontarget organisms; entomopathogen; risk assessment; biological control