Biocontrolator activity of entomogenous fungí against Premnotrypes vorax (Coleoptera: Curculionidae) throught their utilization individual or combined

Abstract

In order to select entomopathogenic isolates against Premnotrypes vorax four isolates of Beauveria bassiana, three of Beauveria brongniartii and one of Metarhizium anisopliae, were evalua­ted under laboratory conditions. Adults of Premnotrypes vorax were treated with a unique concentration containing 1x10⁸ propagules/ml, of each of them, and mortality was evaluated daily. To deter­mine their lethal concentrations 50 (CL_5o) and 90 (CL₉₀) successive concentrations of the selected isolates were used, from 1x10⁵ to 1x10⁹ propagules/ml. Biocontrol activity by a combination of selected isolates of Metarhizium anisopliae and Beauveria bassiana was determined; the bioassay was performed by using the CL50 oí each of them, and comparing the result with the mortality obtained by using twiceCL_SI~of individual isolates. From the eight isolates evaluated Mt.L1 of Metarhizium anisopliae and Bv.L2 of Beauveria bassiana were selected because caused 100% insects mortality after 24 and 25 days respectively. These isolates showed lethal concentrations 50 y 90 of 13x10⁵ and 50x10⁶ propagules/ml, respectively for Mt.L1 and 55x10⁵ and 48x10⁷ propagules/ml, respectively for Bv.L2. The mortality observed in Premnotrypes vorax was significantly superior when the isolates were utilized in combination because produced 100% of mortality ten days after the application, while when the individual activity was evaluated with the isolate Mt.L1 53,33% the mortality was observed and with the isolate Bv.L2 the mortality was of the 43,44%, in the same time.