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Undiagnosed mildew and leaf spot on onion in the Netherlands


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: Wed 6 Oct 2021
Source: FreshPlaza [summ., edited]
https://www.freshplaza.com/article/9361049/dutch-onion-yield-forecast-adjusted-due-to-rain-mildew-leaf-spot-disease/


The Dutch onion yield forecast has been adjusted downwards. An abundance of onions was expected earlier, but now volumes are down due to a combination of heavy rainfall, mildew, and leaf spot disease.

[byline: Izak Heijboer]

--
communicated by:
ProMED
<promed@promedmail.org>

[A large number of fungal, bacterial, and nematode pathogens, as well as several viruses and phytoplasmas, are known to affect onion (_Allium cepa_) and related crops. Most of the major pathogens of this crop are soil borne and favoured by humid conditions.

The diseases include 2 types of mildews: powdery mildew caused by fungi in the genus _Leveillula_; and downy mildew caused by fungus-like oomycetes in the genus _Peronospora_. Leaf spots are associated with a number of diseases affecting the crop; they can be due to either bacteria (such as _Pseudomonas_ or _Xanthomonas_ species), or fungal pathogens (such as _Glomerella_, _Alternaria_ or _Stemphylium_ spp.). It is not clear specifically which of these diseases are referred to above.

Reliable diagnosis of the particular pathogens associated with the problems is needed before any management strategies can be designed.

Maps
Netherlands:
http://healthmap.org/promed/p/104 and
http://www.ezilon.com/maps/images/europe/physical-map-of-Netherlands.gif (with provinces):
Europe, overview:
https://mapofeurope.com/wp-content/uploads/2018/03/europe-political-map.jpg

Pictures
Photo gallery of onion diseases:
http://www.ipmimages.org/browse/AreaSubs.cfm?area=86

Links
List of major diseases and pathogens of onion (and garlic):
https://www.apsnet.org/edcenter/resources/commonnames/Pages/OnionandGarlic.aspx
Information on some onion diseases:
http://www.omafra.gov.on.ca/english/crops/facts/95-063.htm, and
http://vegetablemdonline.ppath.cornell.edu/factsheets/Onions_List.htm
Fungal taxonomy via:
http://www.indexfungorum.org/Names/Names.asp
- Mod.DHA]

See Also

Purple blotch, onion - Nigeria: impact 20210607.8431139
2020
---
Anthracnose, onion - India: (MH) 20201026.7893051
Purple blotch & undiagnosed bulb rot, onion - India: (KA) 20200903.7741820
Anthracnose twister complex, onion - India: (KA) 20200518.7351461
Stemphylium blight, onion - USA: (NY) 20200109.6878794
2019
---
Purple blotch, shallot - India: (TN) 20191208.6829852
2018
---
Blight diseases, coffee & vegetable crops - Kenya 20180604.5837538
Purple blotch, spring onion - Jamaica: (MA, SE) 20180507.5787743
White rot, garlic - China: (SD) 20180419.5758478
Stemphylium blight, onion - New Zealand 20180405.5727825



More news from: ISID (International Society for Infectious Diseases)


Website: http://www.isid.org

Published: October 8, 2021

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