Abstract

The Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say), is one of the major economically pests of potato throughout the world. In this study, the pathogenicity of six isolates of Beauveria bassiana (Bals.) Vuill. (four indigenous and two non indigenous isolates) and two indigenous isolates of Metarhizium anisopliae (Metsch.) were investigated. Five different concentrations from each isolate, 1×10⁷, 5×10⁷, 1×10⁸, 5×10⁸and 1×10⁹ conidia ml^-1, were applied in bioassays on 2nd and 4th instars larvae. Results showed that the percentage of mortality due to AKB isolate of B. bassiana at the highest concentration were 78.88 and 44.44, for 2nd and 4th instars larvae, respectively. Also there were significant differences in percentage of mortality between AKB and other treatments. Other isolates, LRC107, IRAN429C, LRC137, IRAN441C and Z-1 were scored in the subsequent classes, respectively. Both M. anisopliae isolates, DEMI001 and IRAN437C showed the lowest mortality rate on larvae in comparison with B. bassianaisolates. In all experiments, with increase in conidial concentration, the mortality rate was increased. Based on our results, the 2nd instar larvae were more susceptible than the 4th instar.

Key words: Biological control, Beauveria bassiana, Metarhizium anisopliae, Leptinotarsa decemlineata.