Symptoms of the disease can differ among hosts but generally include reduced root volume and function, leading to stunting and chlorotic foliage.

Aphanomyces root rot is an important agricultural disease in the United States, Europe, Australia, New Zealand, and Japan.

Because A. euteiches is a root-infecting pathogen, primary symptoms occur on roots and stem tissue below the soil line.

Symptoms in the above-ground plant tissue can include chlorosis of the cotyledons and necrosis of the epicotyls and/or hypocotyls, stunting, and wilting of foliage.

[1] Symptoms are generally similar among infected legumes, however timing and pattern of disease can differ among hosts and between annuals and perennials.

In both peas and beans, lesions tend to progress up the plant tissue, starting with the epicotyls and moving to the hypocotyls, eventually extending above the soil.

Lesions on beans, on the other hand, have a characteristic water-soaked appearance, are grayish-green in color, and are firm to the touch.

[1] A. euteiches exhibits no macroscopic signs, but oogonia and oospores can be seen in root tissue with a compound microscope.

After direct or indirect germination, coenocytic hyphae of A. euteiches colonize host tissue through inter- and intra-cellular growth.

[1] Because Aphanomyces euteiches is homothallic the antheridium and oogonium arise from the same hypha and are self-compatible, meaning separate mating types are not needed for sexual reproduction.

[1][11][12] At the time, the disease had plagued Wisconsin and the American Midwest, where monoculture was commonplace in pea production for processing, for decades.

[1][11][13] The pathogen has since been recorded in Europe, Australia, New Zealand, Japan, and throughout the United States, suggesting that the disease may have already been widespread at the time of its discovery.

In agricultural regions that produce large amounts of susceptible crops and have favorable weather conditions for A. euteiches, careful monitoring is of paramount importance.

In fact, prevalence of Aphanomyces root rot has ultimately shifted pea production in the United States from being predominantly in the Midwest and Eastern parts of the country to drier states such as Idaho, Washington, and Oregon where A. euteiches is still common but conditions are less favorable.

[1][13] In addition to fresh peas, alfalfa is another crop where Aphanomyces root rot (ARR) causes significant economic damage.

[1] Since then, Aphanomyces root rot has been an emerging concern in alfalfa crops in the United States and Canada, and is considered widespread in Wisconsin.