Phytophthora capsici is an oomycete plant pathogen that causes blight and fruit rot of peppers and other important commercial crops.

It was first described by L. Leonian at the New Mexico State University Agricultural Experiment Station in Las Cruces in 1922 on a crop of chili peppers.

[2] P. capsici has a wide range of hosts including members of the families Solanaceae and Cucurbitaceae as well as Fabaceae.

Under field conditions, P. capsici has been found to affect a wide range of hosts in the families Cucurbitaceae, Fabaceae, and Solanaceae, including: cantaloupe, cucumber, watermelon, bell pepper, tomato, snap beans, and lima beans.

[5] Infection of the pepper commonly starts at the soil line leading to symptoms of dark, water soaked areas on the stem.

Leaf spots start out small and become water soaked, and as time progresses may enlarge turn tan and crack.

[5] Solanum lycopersicum: P. capsici can cause crown infections, leaf spot, and foliar blight in tomato.

[5] Foliar blight with rapidly expanding water soaked regions and fruit rot are common symptoms on susceptible species of summer and winter squash varieties.

Chlamydospores, found in other Phytophthora species, have not been documented on P. capsici in nature or formed on isolates that were collected from a range of hosts and locations.

Crops should also avoid conditions that would be conducive to the pathogen by using well drained soils and raised beds.

[3] As stated above, "Excess moisture is the single most important component to the initial infection and subsequent spreading of Phytophthora capsici.

[10] Mefenoxem is the active enantiomer contained in the racemic fungicide metalaxyl used to defend against Phytophthora capsici.

Sexual recombination provides the genetic diversity to promote resistance towards fungicides in P. capsici.

[13] Phytophthora capsici was first described by Leon H. Leonian at the New Mexico Agricultural Research Station in Las Cruces in 1922.