A ProMED-mail post <http://www.promedmail.org>
ProMED-mail is a program of the International Society for Infectious Diseases <http://www.isid.org>
Date: Mon 26 Feb 2018
Source: Grainews [edited]
<https://www.grainews.ca/2018/02/26/managing-aphanomyces-and-root-rot-in-pulse-crops/>
Aphanomyces root rot 2017 survey results showed a high prevalence in Prairie pulse crops . Agriculture and Agri-Food Canada's Syama Chatterton says she found root rot in every field, making prevalence an alarming 100 per cent. "As for the percentage of roots that have disease within a field, we're looking at about 70 per cent," she said.
In terms of severity, roots are rated on a scale with 1 being healthy and 7 the most diseased. Peas, said Chatterton, were at about 3 to 3.3 across all roots in Alberta, Saskatchewan and Manitoba with little variations in some regions.
Lentils saw a lot less root rot, about 20 to 30 per cent incidence, even though prevalence was at 100 per cent. Severity came in at 2 on average. "I think that was due to drier conditions in the lentil growing areas in 2017." The number of fields that were positive for aphanomyces in lentils [were] roughly 10 per cent, in peas roughly 40 per cent.
[byline: Melanie Epp]
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communicated by: ProMED-mail <promed@promedmail.org>
[Aphanomyces (or common) root rot (ARR) of peas is caused by the fungus-like organism (oomycete) _Aphanomyces euteiches_ f.sp. _pisi_.
It is considered the most devastating disease of peas worldwide, with average yearly losses of 10 per cent although entire fields may be destroyed when conditions are favourable for the disease. The pathogen can also affect other legumes such as lentils and lucerne, but not beans which are only susceptible to f.sp. _phaseoli_. Symptoms may include discoloured, water soaked areas on lower stems and roots expanding to extensive rot of the whole root system. Affected plants develop stunting, wilting and yellowing of the crown and often die prematurely. These symptoms are similar to other root rots caused, for example, by species of _Fusarium_, _Rhizoctonia_ or _Pythium_ and this may lead to ARR being misdiagnosed. ARR can infect crops at any stage and disease development is favoured by waterlogged soils.
ARR is soil borne and oospores can survive in the soil for 10 years or more. The pathogen is spread with plant material (including plant debris and volunteer crop plants), mechanical means (including contaminated equipment), wind and water. Disease management is difficult but may include long crop rotations to slow down build-up of soil inoculum, field drainage, chosing fields with low oospore soil load and removal of inoculum sources (such as crop debris). Fungicide seed treatments may be effective but are subject to strict regulations in many countries. Some ARR resistance has been identified in pea germplasm, but no highly resistant commercial cultivars are available.
In Canada, another pea root rot due to _Fusarium_ species is widely distributed. Coinfection with both pathogen leads to more severe disease and is therefore of special concern.
Other species in the genus cause serious, economically important diseases of sugar beet (_A. cochlioides_) and radish (_A. raphani_).
Maps
Canada (with states):
<http://www.lib.utexas.edu/maps/americas/canada_pol_1986.gif>
Pictures
ARR symptoms on pea:
<https://static.producer.com/wp-content/uploads/2014/03/53_3col_aphanomyces_Leoville-soil-normal-water-sterile-vs-non-sterile-copy.jpg>,
<https://www.apsnet.org/edcenter/intropp/lessons/fungi/Oomycetes/Article%20Images/Aphanomyces02.jpg>,
<http://bit.ly/2FKN7UQ>,
<https://www.apsnet.org/edcenter/intropp/lessons/fungi/Oomycetes/Article%20Images/Aphanomyces17.jpg>
(compared to healthy),
<https://www.topcropmanager.com/media/k2/items/cache/3c3a92fc5148222a95e3938433e3c21c_XL.jpg>
and
<https://static.agcanada.com/wp-content/uploads/sites/3/2016/02/aphanomyces-update-jblair_c.jpg>
(affected field)
ARR on lucern:
<https://www.extension.umn.edu/agriculture/forages/pest/yellow-alfalfa/img/aphanomyces-uiuc.jpg>
and
<https://fyi.uwex.edu/forage/files/2017/04/Screen-Shot-2017-04-14-at-12.39.04-AM.png>
(compared to healthy)
Links
Information on ARR:
<https://www.apsnet.org/edcenter/intropp/lessons/fungi/Oomycetes/Pages/Aphanomyces.aspx>,
<https://www.2020seedlabs.ca/aphanomyces-root-rot-in-peas/>,
<https://pnwhandbooks.org/plantdisease/host-disease/pea-pisum-sativum-aphanomyces-root-rot>,
<https://www.topcropmanager.com/inoculants/another-root-rot-18564>
and
<http://www.omafra.gov.on.ca/english/crops/field/news/croptalk/2007/ct-1107a3.htm>
ARR pathogen information:
<http://www.plantwise.org/KnowledgeBank/Datasheet.aspx?dsid=6408> and <https://www.2020seedlabs.ca/wp-content/uploads/2017/05/TB-aphano-fig2-v2.jpg>
(life cycle)
ARR in Canada:
<https://www.topcropmanager.com/diseases/aphanomyces-root-rot-expanding-across-western-canada-19989>
and
<http://www1.agric.gov.ab.ca/$Department/deptdocs.nsf/all/crop15187/$FILE/syama-chatterton-pea-root-rot-in-alberta-2015.pdf>
_A. euteiches_ f.sp. _pisi_ taxonomy:
<http://www.indexfungorum.org/names/NamesRecord.asp?RecordID=118294>
- Mod.DHA]
[See Also:
2004
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Pythium irregulare, lentil - USA (WA): first report
http://promedmail.org/post/20040219.0533
2002
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Rhizoctonia oryzae, pea, first report - N. America http://promedmail.org/post/20020516.4225]
Topics
Species
