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Date: Mon 17 Oct 2022
Source: The New Indian Express [summ. Mod.DHA, edited]
https://www.newindianexpress.com/states/tamil-nadu/2022/oct/17/rain-induced-basal-rot-plays-hits-shallot-harvest-in-perambalur-2508864.html


Basal rot, a disease caused by fungi and bacteria, took a toll on shallot crops in Perambalur district. This [2022] is the 3rd consecutive year of the disease affecting yield. Shallot was grown on more than 2000 hectares in the district in 2022.

Farmers say recent heavy rains led to the infection. They say that the fungal attack is a usual phenomenon every rainy season. In some areas, crops get completely destroyed by the disease. Farmers are calling on authorities to come up with a solution since they are running out of seed onions.

The Department of Horticulture in the district said that farmers, in order to prevent the disease, need to practice crop rotation. They said that they have been raising awareness among farmers about this method.

[Byline: P Thiruselvam]

--
Communicated by:
ProMED

[A number of fungi can affect onion (_Allium cepa_; some varieties known as shallots) and related crops such as garlic (_A. sativum_) to cause root and basal rots. The term 'basal rot' is mostly used for species of _Fusarium_. Species of _Phoma_, _Pythium_, _Rhizoctonia_, as well as some nematodes have also been reported to be associated with root rot symptoms. There are also several bacteria causing root rots in the crop, including species of _Pseudomonas_, _Dickeya_, and _Pantoea_.

Root rot diseases are usually soilborne and also spread with infected plant and other materials, including agricultural implements. They are generally favoured by wet conditions and are difficult to control. Disease management may include deep plowing, phytosanitation, and crop rotations of several years. For fungal rots, appropriate fungicide regimes may be helpful, but agrochemicals are often of limited use for soil-borne pathogens.

While a possible contribution of both fungi and bacteria to the rotting problems is mentioned above, specific identification of any pathogens involved does not seem to have been carried out.

Maps
India (with states):
https://www.worldometers.info/img/maps/india_physical_map.gif
Tamil Nadu districts:
https://i.pinimg.com/736x/26/75/6d/26756d256f9b2e294baa3fc6fa09bb1e.jpg

Pictures
Root and basal rots of onion:
https://www.mtvernon.wsu.edu/path_team/DiseaseGallery/onion-fusarium-basal-rot-5L.jpg,
https://res.cloudinary.com/growinginteractive/image/upload/q_80/v1512747965/Diseases/onion-fusarium-basal-rot-2.jpg,
https://res.cloudinary.com/growinginteractive/image/upload/q_80/v1512747970/Diseases/onion-fusarium-basal-rot.jpg and
https://www.mtvernon.wsu.edu/path_team/DiseaseGallery/dg91L.jpg (affected field)
Basal rot of garlic:
https://pnwhandbooks.org/sites/pnwhandbooks/files/plant/images/garlic-allium-sativum-basal-rot/acfuaa005659.jpg

Links
Information on onion basal rot:
https://www.cabi.org/isc/datasheet/24624,
https://www.growveg.co.uk/plant-diseases/uk-and-europe/onion-fusarium-basal-rot/,
https://pnwhandbooks.org/plantdisease/host-disease/onion-allium-cepa-fusarium-basal-rot,
https://doi.org/10.1080/03235408.2019.1672913 and
https://wegrowfortheworld.com/2016/09/fusarium-basal-plate-rot-of-onion-in-2016/
Other major root rot pathogens of onion (and garlic) via:
https://www.apsnet.org/edcenter/resources/commonnames/Pages/OnionandGarlic.aspx
Fungal taxonomy via:
http://www.indexfungorum.org/Names/Names.asp
Bacterial taxonomy via:
http://www.uniprot.org/taxonomy/
- Mod.DHA

ProMED map:
Tamil Nadu State, India: https://promedmail.org/promed-post?place=8706258,319]

See Also

2021
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Basal rot, onion - India: (TN) 20211124.8699847
Undiagnosed root rot, onion - India: (TN) 20210202.8156911
2020
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Purple blotch & undiagnosed bulb rot, onion - India: (KA) 20200903.7741820
2019
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Purple blotch, shallot - India: (TN) 20191208.6829852
2016
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Root rot, garlic - Bangladesh: (BA) 20160325.4117622
2015
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Undiagnosed fungus, garlic - India: (KL) 20150904.3623031
2011
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Stem & bulb nematode, garlic - USA: (NY) 20111117.3388
Potato rot nematode, garlic - Canada: (ON) 20110825.2589
and additional items on root diseases of _Allium_ crops in the archives

Website: http://www.isid.org

Published: October 21, 2022