Abstract
In order to select entomopathogenous 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 letal concentrations 50 (CL50) and 90 (CL90) successive concentrations of the selected isolates were used, from 1x105 to 1x109 progagules/ml. Biocontrol activity by combination of selected isolates of Metarhizium anisopliae and Beauveria bassiana was determined; the bioessay was performed by using the CL50 of each of them, and comparing the result with the mortality obtained by using twice CL50 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 letal 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.
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