The spectrum and abundance of entomopathogenic fungi in agricultural soil receiving different pesticide applications were evaluated . Seven small field plots within a barley crop were selected . Each plot had received a different pesticide treatment at slightly higher than the field rate each year for the previous 12-19 years . The field plots received either benomyl (fungicide) , triadimefon (fungicide) , aldicarb (insecticide) , chlorfenvinphos (insecticide) , glyphosate (herbicide) , all five of these pesticides or no pesticides at all (control) . Soil sampled from each plot was baited with Galleria mellonella larvae at either 18 or 26 C . Five species of entomopathogenic fungi infected these larvae . Beauveria bassiana was the dominant species , and the only species for which infection levels were high enough to be analyzed statistically . Significantly fewer G. mellonella larvae became infected with B. bassiana in soil treated with benomyl than in other treatments . This deleterious effect was confirmed in in vitro experiments where benomyl inhibited fungal growth significantly . Chlorfenvinphos also reduced the proportion of G. mellonella becoming infected with B. bassiana slightly (although not statistically significantly) . This effect was much greater in in vitro experiments in which chlorfenvinphos inhibited fungal growth significantly . B. bassiana- induced mortality was significantly greater in G. mellonella larvae placed in soil treated with triadimefon than in other treatments . In vitro studies , however , demonstrated that triadimefon inhibited rather than stimulated growth . A similar anomaly between field and laboratory observations was seen in the case of aldicarb . There was no significant difference in the number of G. mellonella larvae found infected with B. bassiana in soil treated with aldicarb than in the control soil . However , in the in vitro studies , aldicarb stimulated fungal growth at all concentrations except 10 times the field rate . In general , significantly fewer larvae became infected with B. bassiana at 26 C than at 18 C in all treatments . Pesticides may have a direct impact on the natural occurrence , infectivity and population dynamics of entomopathogenic fungi . They also affect other macro - and microorganisms in the soil which may interact with the ento mopathogenic fungi . In combination with climate and soil variables , these effects are difficult to separate . Although any suppression of these fungi may be detrimental to their capacity as natural enemies , this study has demonstrated that pesticides used under field conditions are unlikely either to kill all the entomopathogenic fungi present in the treated area or to limit their recolonization . It seems likely , therefore , that pesticides have the potential to be used in conjunction with mycoinsecticides in integrated pest management systems .