[1]: 33 Phytophthora cactorum has an extremely wide host range, and can infect over 200 species or 160 genera of trees, ornamentals, and fruit crops.

Although the symptoms this pathogen produces varies between the types of organisms it infects, in general disease occurs during periods that are both wet and warm.

When infecting apple trees, the organism can attack through wounds either above or below the soil line, impairing phloem and root function, and causing stunting, foliar disorders, and death after several years.

Foliar disease of ginseng usually occurs during May and early June, causing the leaves to become transparent and papery.

Ginseng foliar infection occurs through the rain splash dispersal of spores from the soil onto above ground wounds.

Although the size may vary based on the environmental conditions in which they are formed, the width of a sporangia is always more than 2/3 times than its length.

The minimum amount of time the plant must be saturated to produce an infection depends on factors such as genetics, physiological processes, and the environment.

However, when a plant is allowed to sit in soil that is heavy and soggy for long periods of time, the chance of infection is increased.

A plant's inability to fight off the pathogen is impeded when saturated soil conditions limit the amount of available oxygen for its roots.

In many cases, most host plants are the most susceptible to infection during spring and autumn when the soil is wetter and at a more ideal temperature for zoospore production and activity.

[citation needed] The importance of this oomycete is its vast host range and the damage it causes to major crops.

This pathogen can cause root rot that stunts the host's growth and damages vascular tissue, which is especially detrimental to pear and apple orchards.

These fertilizers include organic materials that release ammonia, nitrous acid, and amendments to reduce the pH to less than 4.

[7] The use of raised beds and a carefully managed drip irrigation system will be important cultural practices that can be implemented.

Within the plant, the P. cactorum phytotoxin is most likely xylem transported through and can accumulate in the space in between leaves where it causes desiccation and withering.

[13] A toxin protein similar to other oomycete elicitins based on apparent molecular weight, isoelectric point, amino acid composition, and host pathology induction activity was isolated from P. cactorum culture.