Articles

Metarhizium anisopliae biopesticides and fungus isolates: control efficacy against Rhynchophorus ferrugineus (Olivier) (Coleoptera Dryophthoridae) on different contamination substrata.


Abstract


The lack of biological insecticides based on Metarhizium anisopliae (Metsch.) Sorokin registered in Italy for the control of the Red Palm Weevil (RPW), Rhynchophorus ferrugineus (Olivier), prompted studies to evaluate the efficacy of two commercial products, Met52® and BioStormTM and of their fungal isolates, M. anisopliae (Man52) and (ManBS) respectively, against the adults. The virulence of the M. anisopliae strains (Man52) and (ManBS) was compared with that of an indigenous M. anisopliae (Man08/I05) strain obtained from R. ferrugineus specimens collected in the wild and that showed to be very virulent against the RPW in previous studies. In both tests the sublethal effects of the treatments on female reproductive potential were examined in relation to the infective substratum. Laboratory results indicated that the commercial formulations mixed directly into the soil were not active in transmitting the infection to RPW adults and in reducing female fecundity and fertility. Diversely the fungal M. anisopliae (ManBS), (Man52) and (Man08/I05) strains inoculated on a rice substratum caused over 80% mortality of the phytophagous. In particular, M. anisopliae (ManBS) and the M. anisopliae (Man08/I05) produced the highest mortality (100%), with LT50 e LT90 reached in 3 and 6 days respectively. M. anisopliae (Met52) strain instead led to 85% mortality of RPW specimens in 28-days but it took longer to reach LT50 (6 days) and LT90 (12 days). The reproductive potential of females infected with the fungal strains was also significantly reduced with respect to the control. This study indicates the possibility of using also M. anisopliae strains in use against other insects of agricultural importance, for the control of R. ferrugineus although their effectiveness is conditioned by the formulations and/or methods employed against the RPW.


Keywords

RPW adults; entomopathogenic fungus; virulence; microbiological control

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