Mildew

 (Downy mildew)

• "Pseudofungi" obligate parasites belonging to the Oomycetes*.
• Internal mycelium evolving in the leaf parenchyma sending suckers into the cells.
• Sporangiophores emerging through stomata and producing sporangia capable of germinating and/or producing zoospores (asexual reproduction). The sexual reproduction is materialized by the formation of oospores rather rarely observed.
• Typical symptoms: rapidly spreading leaf spots, brown lesions on stems, fruit rots, etc.
• Several mildews are likely to attack tropical vegetable crops; they are classified in several genera: Pseudoperonospora , Phytophthora , Bremia , etc. Let us add that Pythium spp. , and white rust agents belong to the Oomycetes.

* Mildew agents are part of the Oomycetes, a group that includes more than 800 saprophite or parasitic species long previously classified in the Phycomycetes or "lower fungi" (Eumycetes). This classification was called into question a few years ago because their ultra structure, their biochemistry and their molecular sequences indicated that they were close in particular to algae (green and brown), diatoms…. Currently, depending on the bibliographical sources, these "water molds" are associated with the reign of the Chromista (Index fungorum) or the Stramenopila (Heterokontes) (Tree of life).