When the ability of the cells of a plant to carry out one or more of these essential functions is interfered with by either a pathogenic organism or an adverse environmental factor, the activities of the cells are disrupted, the cells malfunction or die, and the plant becomes diseased. Tens of thousands of diseases affect cultivated and wild plants. Plant diseases are grouped according to the type of pathogen that causes the disease. All plants are attacked by some kinds of fungi, and each of the parasitic fungi can attack one or many kinds of plants Fungi are small, generally microscopic, eukaryotic, usually filamentous, branched, spore-bearing organisms that lack chlorophyll. Fungi cause local or general symptoms on their hosts and such symptoms may occur separately or concurrently or may follow one another. Medicinal plants like other plants have specific fungal diseases. In this chapter, considering the importance of fungal diseases on this group of plants, we review some of the most important fungal diseases of the number of medicinal plants.
