Planting of flowers and ornamental plants, due to the presence of various climates and suitable weather condition, are great importance in Iran. According to the International Center of Ornamental Flowers and Plants (AIPH), Iran has the 12th place in terms of cultivating flowers and ornamental plants among the other countries, which exports of these plants compared to the area under cultivation of flowers and Ornamental plants have a very low number, unfortunately. One of the challenges of producing and exporting these plants is the lack of attention to the pests and disease of plants such as powdery mildew in Iran. The presence of these fungi on ornamental plants often reduces the beauty and marketability of these plants. Fungi which cause Powdery mildews (Ascomycota: Erysiphales) are one of the most widespread and recognizable plant disease. In order to identify the species, taxonomic issues and host range of Powdery mildews of ornamental plants in Esfahan, Chaharmahal o bakhtiari, Markazi and Lorestan provinces, a comprehensive sampling have been done during 2017-2018.Collected samples after transferring to the Mycology laboratory and host plant determination, morphological characteristics of its powdery mildew were studied using valid identification keys. Totally, 21 species belonged to 6 genus were identified and described. These species were included:
Erysiphe australiana, Erysiphe convolvuli, Erysiphe howeana, Erysiphe polygoni, Erysiphe multappendicis, Erysiphe quericicola, Erysiphe rayssiae, Erysiphe robiniae, Erysiphe trifolii, Euoidium cf. agerati, Golovinomyces ambrosiae,Golovinomyces biocellatus, Golovinomyces cichoracearum, Golovinomyces orontii, Leveillula papilionacearum, Leveillula taurica, Podosphaera leucotricha, Podosphaera maculari, Podosphaera xanthii, Podosphaera pannosa, Sawadae bicornis.
Among identified specimens Leveillula taurica on Cleome sp.and Catharanthus roseus and Silybum marianum، Golovinomyces biocellatus on Mentha pipperita and Nonea sp.، Podosphaera maculari on Fragaria vesca and Golovinomyces ambrosia on Rudbeckia hirta are newly reported on theses host plant fron Iran.