PATHOGENICITY OF ENTOMOPATHOGENIC FUNGI AGAINST Sitophilus granarius (L.) (COLEOPTERA: CURCULIONIDAE) UNDER ABIOTIC FACTORS

Present bioassays were conducted to determine the effect of temperature and relative humidity (r.h.) on the pathogenicity of two commercially available formulations of entomopathogenic fungi (EPF) i.e. Metarhizium anisopliae and Beauveria bassiana against Sitophilus granarius (L.). Adults of S. granarius were exposed to three conidial concentrations (1 x 10(8), 1.5x 10(8) and 2x 10(8) CFU kg(-1) of wheat grains) of each EPF at three temperature ranges (25, 30 and 35 degrees C) and relative humidity levels (45, 60 and75%). Pathogenicity was assessed after 7, 14 and 21days (d) and after last count of 21 d all adults were removed from the vials and vials were maintained at same conditions for additional 60 d to assess the F-1 adult progeny development. Results showed that efficacy of EPF influenced by temperature, relative humidity, conidial concentration and exposure period. In case of B. bassiana pathogenicity was increased with reduced temperature 25 degrees C and moderate r.h. 60% and reached up to 72.5% at higher tested conidial concentration after 21 d of exposure period. For M. anisopliae optimum conditions for pathogenicity were moderate temperature (30 degrees C) and r.h. (60%) at which maximum pathogenicity of 64.16% was achieved after 21 d with highest concentration. Regarding progeny production, reduced level of r.h. (45%) significantly suppressed the adult emergence with all tested levels of temperature for both EPFs. However, least numbers of adults were emerged on those abiotic conditions where higher pathogenicity was noticed. Overall results illustrated that both EPF have potential to control S. granarius but their efficacy highly dependent on abiotic factors and these factors should be seriously considered when planning an IPM program based on EPF.