Editing Onion (section)

=== Pests and diseases ===

Onions suffer from several pests and diseases. The most serious for the home gardener are likely to be the [[onion fly]], stem and bulb eelworm, white rot, and neck rot. Diseases affecting the foliage include rust and smut, downy mildew, and white tip disease. The bulbs may be affected by splitting, white rot, and neck rot. Shanking is a condition in which the central leaves turn yellow and the inner part of the bulb collapses into an unpleasant-smelling slime. Most of these disorders are best treated by removing and burning affected plants.<ref name=Hessayon>{{cite book |title=Be your own Vegetable Doctor |last=Hessayon |first=D.G. |author-link=D. G. Hessayon |year=1978 |publisher=[[Pan Britannica Industries]] |isbn=978-0-903505-08-6 |pages=22–23}}</ref> The larvae of the onion leaf miner or leek moth (''[[Acrolepiopsis assectella]]'') sometimes attack the foliage and may burrow down into the bulb.<ref>{{cite journal |last=Landry |first=Jean-François |s2cid=86748199 |year=2007 |title=Taxonomic review of the leek moth genus ''Acrolepiopsis'' (Lepidoptera: Acrolepiidae) in North America |journal=The Canadian Entomologist |volume=139 |issue=3 |pages=319–353 |doi=10.4039/n06-098}}</ref>

The onion fly (''Delia antiqua'') lays eggs on the leaves and stems and on the ground close to onion, shallot, leek, and garlic plants. The fly is attracted to the crop by the smell of damaged tissue and is liable to occur after thinning. Plants grown from sets are less prone to attack. The larvae tunnel into the bulbs and the foliage wilts and turns yellow. The bulbs are disfigured and rot, especially in wet weather. Control measures may include crop rotation, the use of seed dressings, early sowing or planting, and the removal of infested plants.<ref>{{cite web |url=http://www.agroatlas.ru/en/content/pests/Delia_antiqua/ |title=''Delia antiqua'' (Meigen): Onion Fly |website=Interactive Agricultural Ecological Atlas of Russia and Neighboring Countries |access-date=2013-03-29 |archive-date=14 May 2013 |archive-url=https://web.archive.org/web/20130514095654/http://www.agroatlas.ru/en/content/pests/Delia_antiqua/ |url-status=live }}</ref>

The onion eelworm (''[[Ditylenchus dipsaci]]''), a tiny parasitic soil-living [[nematode]], causes swollen, distorted foliage. Young plants are killed and older ones produce soft bulbs. No cure is known and affected plants should be uprooted and burned. The site should not be used for growing onions again for several years and should also be avoided for growing [[carrot]]s, [[parsnip]]s, and [[bean]]s, which are also susceptible to the eelworm.<ref>{{cite web |url=http://www.gardenaction.co.uk/techniques/pests/onion_eelworm.htm |title=Onion Eelworm (''Ditylenchus dipsaci'') |year=2011 |website=GardenAction |access-date=2013-03-29 |archive-date=3 February 2013 |archive-url=https://web.archive.org/web/20130203011252/http://www.gardenaction.co.uk/techniques/pests/onion_eelworm.htm |url-status=live }}</ref>

White rot of onions, leeks, and garlic is caused by the soil-borne fungus ''[[Stromatinia cepivora|Sclerotium cepivorum]]''. As the roots rot, the foliage turns yellow and wilts. The bases of the bulbs are attacked and become covered by a fluffy white mass of [[Mycelium|mycelia]], which later produces small, globular black structures called [[Sclerotium|sclerotia]]. These resting structures remain in the soil to reinfect a future crop. No cure for this fungal disease exists, so affected plants should be removed and destroyed and the ground used for unrelated crops in subsequent years.<ref>{{cite web |url=https://www.rhs.org.uk/advice/profile?pid=226 |title=Onion white rot |website=RHS Gardening |publisher=Royal Horticultural Society |access-date=2013-03-29 |archive-date=4 August 2018 |archive-url=https://web.archive.org/web/20180804231507/https://www.rhs.org.uk/advice/profile?pid=226 |url-status=live }}</ref>

Neck rot is a fungal disease affecting onions in storage. It is caused by ''[[Botrytis allii]]'', which attacks the neck and upper parts of the bulb, causing a grey mould to develop. The symptoms often first occur where the bulb has been damaged and spread down the affected scales. Large quantities of [[spore]]s are produced and crust-like sclerotia may also develop. In time, a dry rot sets in and the bulb becomes a dry, mummified structure. This disease may be present throughout the growing period, but only manifests itself when the bulb is in storage. Antifungal seed dressings are available and the disease can be minimised by preventing physical damage to the bulbs at harvesting, careful drying and curing of the mature onions, and correct storage in a cool, dry place with plenty of circulating air.<ref>{{cite web |url=https://www.rhs.org.uk/advice/profile?PID=747 |title=Onion neck rot |website=RHS Gardening |publisher=Royal Horticultural Society |access-date=2013-03-29 |archive-date=4 August 2018 |archive-url=https://web.archive.org/web/20180804231835/https://www.rhs.org.uk/advice/profile?PID=747 |url-status=live }}</ref>

<gallery class=center mode=nolines widths=180 heights=180>
File:Uienvlieg maden.jpg|Larvae of the [[onion fly]]
File:Urocystis colchici var. cepulae on an onion seedling.jpg|Onion smut, ''Urocystis colchici'' var. cepulae, on a seedling
File:Zwiebel Blattfleckenkrankheit (Cladosporium allii-cepae) Anamorph - Noé López G.LLG-Bernburg.jpg|Onion leaf spot caused by ''[[Cladosporium|Cladosporium allii-cepae]]''
File:Onion (Allium cepa) Bacterial soft rot (42052268015).jpg|Bacterial soft rot caused by ''[[Erwinia carotovora]]'' subsp. carotovora
File:Zwiebel Schmutzfleckenkrankheit (Colletotrichum dematium f. sp. circinans) - G-Bedlan, Wien.jpg|[[Anthracnose]] caused by ''[[Colletotrichum dematium]]'' subsp. circinans
</gallery>

Onion oil is authorised for use in the European Union for use as a pesticide against [[carrot fly]] in [[Apiaceae|umbelliferous crops]] (carrots, parsnips, parsley, celery, celeriac).<ref>{{Cite web |last=European Commission |date=20 July 2018 |title=Final Review report for the basic substance Onion Oil finalised in the Standing Committee on Plants, Animals, Food and Feed at its meeting on 20 July 2018 in view of the approval of onion oil as basic substance in accordance with Regulation (EC) No 1107/2009 |url=https://mst.dk/media/171096/review-report-for-onion-oil-juli-2018.pdf |url-status=live |archive-url=https://web.archive.org/web/20211123111251/https://mst.dk/media/171096/review-report-for-onion-oil-juli-2018.pdf |archive-date=23 November 2021 |access-date=23 November 2021}}</ref>

{|class="wikitable" style="float:right; clear:left; width:14em; text-align:center;"
! colspan=2|Production of onions and shallots (green) in 2022
|-
! style="background:#ddf; width:75%;"|Country
! style="background:#ddf; width:25%;"|<small>[[tonne]]s</small>
|-
|{{CHN}}||864,488
|-
|{{MLI}}||610,576
|-
|{{ANG}}||558,480
|-
|{{JAP}}||510,462
|-
|'''World''' ||'''4,970,615'''
|-
|colspan=2|<small>Source: [[UN Food and Agriculture Organization]]<ref name="faostat">{{cite web |url=http://www.fao.org/faostat/en/#data/QC |title=Production of onions and shallots (green) in 2022: Crops/World Regions/Production Quantity/Year from pick lists |publisher=United Nations Food and Agriculture Organization, Statistics Division (FAOSTAT) |date=2024 |access-date=22 May 2024 }}</ref></small>
|}