The present work aimed at investigating diversified organic treatment including sewage sludge on the insecticide activity of enthomopathogenic fungi and nematodes. Crude sludge from biological tannery sewage treatment plant and vermicomposts based on the sludge with added straw and fruit tree leaves were used for the experiment. Organic treatment significantly affected pathogenic properties of enthomopathogenic nematodes naturally present in the soil of the investigated plots. The highest death rate among trap insects was detected in the soil from untreated plots or fertilised by farmyard manure and vermicomposts. Nematodes from examined plots reproduced in varying numbers depending on the treatment applied on individual plots. The lowest number of invasive larvae was obtained for nematodes from plots fertilised by straw vermicompost, (crude)sewage sludge and hair. The applied organic treatment influenced also insecticide activity of the applied nematodes towards G. mellonella larvae. The highest death rate of G. mellonella larvae was observed in the soils treated with organic fertilisers and farmyard manure. Clear decrease in B. bassiana pathogenic properties was detected in soil fertilised with sewage sludge and hair. Chemical sludge and fertilisation with hair caused also a clear decrease in S. carpocapsae pathogenic properties towards G. mellonella larvae. The obtained results reveal unfavourable effects of crude sewage sludge on the pathogenic properties of enthomopathogenic fungi and insects. Vermicomposts obtained from this sludge revealed a positive influence on the microorganisms. This fact may indirectly improve health conditions of plants.