See text Phytophthora (from Greek φυτόν (phytón), "plant" and φθορά (phthorá), "destruction"; "the plant-destroyer") is a genus of plant-damaging oomycetes (water molds), whose member species cause economic losses on crops worldwide, as well as environmental damage in natural ecosystems.

P. cinnamomi, though, infects thousands of species ranging from club mosses, ferns, cycads, conifers, grasses, lilies, to members of many dicotyledonous families.

[3] The soya bean root and stem rot agent, P. sojae, caused longstanding problems for the agricultural industry.

In general, plant diseases caused by this genus are difficult to control chemically, thus the growth of resistant cultivars is the main management strategy.

[7] In 2019, scientists in Connecticut were conducting experiments testing various methods to grow healthier Fraser trees when they accidentally discovered a new species of Phytophthora, which they called P. abietivora.

Sporangia may be retained by the subtending hyphae (noncaducous) or be shed readily by wind or water tension (caducous) acting as dispersal structures.

[9] Phytophthora is sometimes referred to as a fungus-like organism, but it is classified under a different clade altogether: SAR supergroup (Harosa) (also under Stramenopila and previously under Chromista).