Importance
Pea (Pisum sativum) is the crop where Aphanomyces causes the greatest economic damage. Aphanomyces root rot can account for yearly losses of about 10% in the fields where it occurs, and may cause losses of entire fields in conditions that are favorable to the pathogen. In agricultural regions that produce large amounts of susceptible crops and have favorable weather conditions for A. euteiches, careful monitoring is of paramount importance. Such regions include the American Midwest, particularly the Great Lakes region. In areas where peas are grown for processing, widespread Aphanomyces infection can cause processing (canning) factories to relocate, a considerable threat for local economies. 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.
In addition to fresh peas, alfalfa is another crop where Aphanomyces root rot (ARR) causes significant economic damage. In peas, A. euteiches is the only pathogen that causes Aphonomyces root rot, but in alfalfa a complex of pathogens are often involved in the disease, including Fusarium and Pythium spp. Thus although A. euteiches had been known as a pathogen of pea since the 1920s, it was not until the 1980s that scientists from the University of Wisconsin confirmed it as a significant pathogen of alfalfa.
In alfalfa, A. eutiches is especially damaging in conjunction with Phytophthora medicaginis, which causes Phytophthora root rot (PRR) in alfalfa. After initial studies in Wisconsin, A. euteiches was identified as an economically significant alfalfa pathogen in other states as well. In Wisconsin, Iowa and Kentucky it often exceeds P. medicaginis in prevalence in fields where alfalfa is grown. Due to these diseases, conventional advice was to avoid growing alfalfa in any wet soils. However, with the development of ARR- and PRR-resistant varieties, wet soil conditions have become less of a concern for alfalfa production, at least as far as disease pressure is concerned. Today, modern alfalfa varieties are required to have both PRR and ARR resistance.
Read more about this topic: Aphanomyces Euteiches F.sp. Pisi
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