Crude aqueous and methanolic extracts of 97 plant species belonging to 35 families collected from the west of Iran were screened for antifungal activity against economically important phytopathogenic fungi, Pythium aphanidermatum. Bioassay of the extracts was conducted by paper disc diffusion method on agar plate cultures with four replications. Seventeen of 97 (17.5%) plant species showed inhibitory activity against the tested fungi. Centaurea sp., Papaver dubium, C.behen, C.depressa, Hypericum perforatum, C.iberica, Juglans regia, Vaccaria pyramidata, Mespilus germanica, Verbascum sp., Avena sativa, Alhagi camelrum, H. scabrum, GÃ?â?¢Ã?â??lycyrrhiza glabra, Haplophylum perforatum, Xanthium strumarium and Portulaca oleraceae were the active plant species against P.aphanidermatum. The efficacy of the selected plant crude extracts against P. aphanidermatum was also evaluated in greenhouse condition. All tested plant extracts were superior in reducing the disease severity as compared to the control. Among the different treatments, seed treatments of G. Glabra and P.oleraceae extracts reduced disease severity from 70% for infected control to 43%. This disease severity was reduced to 46% for C.behen. Therefore, weeding and returning these plant species to the soil to retain the soil healthy is a way to reduce phytopathogenic fungi and success in a long-term crop production program. According to these results, we conclude that the flora in the west of Iran can be regarded as a rich source of plants with antifungal activity. Therefore, further screening of other plant species, identifying active fractions or metabolites and application of active extracts under field condition are warranted.
