Oomycetes are not true fungi, as their cell walls are made of cellulose instead of chitin, they are diploid in their vegetative state, and they form coenocytic hyphae (lacking crosswalls).

While this is almost exclusively a plant pathogen, there is one documented case of P. aphanidermatum infecting a human being injured in the Afghanistan conflict.

Symptoms of root rot include stunted growth, chlorotic leaves, leaf drop, and wilting.

The pathogen can cause disease in cool temperatures (55–64 °F) but ideal conditions are between 86 °F and 95 °F,[2] a characteristic which distinguishes it from other Pythium species.

[1][2] High saline content in the soil can promote infection at lower temperature and humidity that is ideal for the pathogen.

The pathogen thrives in a moist environment, so it is important to prevent an excessive amount of moisture from building up in the plant media[4] Irrigation that is too frequent and usage of soil that has poor drainage are common mistakes that result in inoculation.

[1] In addition, poor ventilation and insufficient exposure to sunlight can cause the plants themselves to accumulate moisture, potentially spreading disease.

[2] Sanitation of the soil using chemical treatment and minimizing the amount of plant debris in which the pathogen can survive is also an effective cultural practice.

[2] Several chemical types can be used to manage the pathogen including acylalanines, thiadiazoles, carbamates, cinnamic acid derivatives, phosphonates, and phosphites.

[2][5] Damage caused by Pythium aphanidermatum is difficult to measure because it has such a wide host range and infection results in a variety of symptoms, all of which are detrimental in different ways.

Root infection and seedling damping off are responsible for a decrease in plant health and reduction in yield for economic crops.