Allium cepa
onion
33 Related Pests
Alternaria porri
fungus
Macrosporium porri, Alternaria allii
Worldwide
Widespread
Chile
2024-06-08
Purple blotch is most severe in hot humid onion climates. Has not been reported in Chile
Allium spp.
Yes
Seed as a pathway uncommon. There are only a few reports of Alternaria porri being detected on onion seeds (ALTEPO-1). Gupta and Pathak, 1988 (ALTEPO-6) were not able to show seed contamination by Alternaria porri
Agar plating (ALTEPO-7)
Agar plating
Agar Plating is s standard method of the NSHS
Chemical
Chemical seed treatments and disinfestation methods like hot water are possible but may be phytotoxic; however, newer seed treatment chemicals may be available, so it's advisable to consult with companies supplying these treatments.
Tobacco streak virus
virus
Annulus orae, Asparagus stunt virus, Black raspberry latent ilarvirus, Datura quercina virus, New logan virus, Micotiana virus 8, Nicotiana virus vulaerans, Tobacoo streak ilarvirus, Tracttus orea
Africa: South Africa; Asia: China, India, Iran, Japan; Europe: Denmark, France, Italy, Netherlands, Russia, Serbia, Slovenia, UK; North America: USA; Oceania: Australia, New Zealand; South America: Venezuela
CA, CO, FL, GA, ID, IA, IL, KS, KY, MA, MI, MN, NC, NJ, NY, OH, OK, OR, PA, WA, WI
Korea, Thailand
2025-08-19
Tobacco streak virus is transmitted mainly through infected pollen carried by thrips and by mechanical means. Seed transmission has been reported but occurs inconsistently, making it a minor but possible pathway depending on the host.
Extensive host range includes many weeds, fruit and ornamental plant species. Over 70 species reported as hosts. The vegetables and agronomic crops listed below are important hosts of Tobacco streak virus
No
CABI CPC
Seed as a pathway is not known to occur.
CABI CPC
Crop Protection Compendium. Wallingford, UK: CAB International. www.cabi.org/cpc.
Tomato black ring virus
virus
Lettuce Ringspot Virus, Bean Ringspot Virus, Beet Ringspot Virus, Celery Yellow Vein Virus, Lettuce Ringspot Virus,Potato Bouquet Virus, Potato Pseudo-Aucuba Virus,Tomato Black Ring Nepovirus
Asia: India, Japan, Saudi Arabia, Turkey; Europe: Albania, Belarus, Belgium, Bosnia and Herzegovina, Bulgaria, Croatia, Czechia, Finland, France, Germany, Greece, Hungary, Ireland, Lithuania, Moldova, Netherlands, Norway, Poland, Russia, Serbia, Slovakia, Switzerland, Ukraine, UK
Not known to occur
China, Korea, Mexico, Thailand
2025-08-18
Tomato black ring virus spreads by sap contact, pollen, and seed, with seed transmission confirmed in many crops. Soil nematodes also vector it, though efficiency is low, and the spread in fields is patchy. Seed transmission is the main route for long-distance dispersal and survival between seasons.
Wide host range; however, many are experimental only.
Main: onion, leek, garlic, chive, celery, sugarbeet, cabbage, cauliflower, turnip, pepper, cucumber, lettuce, ryegrass, alfalfa, parsley, tomato, potato, spinach, cowpea.
No
TBRV00-2, TBRV00-3, TBRV00-4, CABI CPC, EPPO
Tomato black ring virus is soil-borne, with onion only rarely reported as a host. Older literature cites seed transmission, but not in Allium cepa, and no evidence supports seed as a pathway
TBRV00-2, TBRV00-3, TBRV00-4, CABI CPC, EPPO
Lister RM, Murant AF, 1967. Seed-transmission of nematode-borne viruses. Annals of Applied Biology, 59:49-62.
Murant AF, Lister RM, 1967. Seed-transmission in the ecology of nematode-borne viruses. Annals of Applied Biology, 59:63-76.
Murant AF, 1983. Seed and pollen transmission of nematode-borne viruses. Seed Science and Technology, 11:973-987.
Crop Protection Compendium. Wallingford, UK: CAB International. www.cabi.org/cpc.
OEPP/EPPO Global Database - European and Mediterranean Plant Protection Organization
Ditylenchus dipsaci
nematode
Anguillula devastatrix, Anguillula dipsaci, Anguillula secalis, Anguillulina dipsaci,Anguillulina dipsaci var. communis, Ditylenchus allocotus, Ditylenchus amsinckiae, Ditylenchus dipsaci var. tobaensis, Ditylenchus fragariae,Ditylenchus sonchophila, Ditylenchus trifolii, Tylenchus allii Tylenchus devastator, Tylenchus devastatrix
Tylenchus dipsaci, Tylenchus havensteini, Tylenchus hyacinthi, Tylenchus putrefaciens
Worldwide in temperate climates.
Widespread
Brazil
2023-05-05
Ditylenchus dipsaci is known to attack over 450 different plant species, including many weeds. There are approximately 20 biological races known that tend to prefer certain hosts.
Yes
DITYDI-3, DITYDI-5, ISFRPLD
Seed is known to be a pathway.
DITYDI-3, DITYDI-5, ISFRPLD
Sieve Method
CABICPC
Used for research. This method has not been standardized or validated.
Seed fumigation
DITYDI-3, ISFRPLD
Crop rotation with non-hosts and fumigation most effective. Quality seed production practices with inspection.
Burkholderia gladioli pv. allicola
bacterium
Phytomonas allicola, Pseudomonas allicola, Pseudomonas gladioli pv allicola
Asia: Israel; Europe: Slovenia; Oceania: Australia, New Zealand; South America: Brazil.
Not known to occur
China, Korea
2024-11-09
Primarily isolated from soil or wet onion residues.
The only natural host is onion. Artifical inoculation includes iris, tulip, narcissus and carrot
No
PSDMGA-3, ISFRPLD
No references found indicating seed as a pathway for this pathogen.
PSDMGA-3, ISFRPLD
Candidatus phytoplasma asteris
phytoplasma
Aconitum proliferation, Aconitum virescence, Alberta aster yellows, alfalfa stunt, Alstroemeria decline, American aster yellows, Anemone virescence, apple sessile leaf, apricot chlorotic leaf roll, azalea little leaf, banana elephantiasis, basil little leaf, Bermuda grass white leaf, black currant reversion, black pepper yellows, blueberry stunt, broccoli phyllody, Bunias phyllody, cactus virescence, cactus witches'-broom, Calendula virescence, canola yellows, Cardaria phyllody, carrot proliferation, carrot yellows, cassava phyllody phytoplasma, cassava witches' broom, Catharanthus little leaf, Catharanthus virescence, chayote witches'-broom, cherry bunch leaf, cherry little leaf, chlorantie, Chrysanthemum witches'-broom, Chrysanthemum yellows, Cirsium stunt, Cirsium yellows, clover phyllody, columbine virescence, coorg black pepper yellows, cosmos phyllody, Cyclamen virescence, dandelion yellows, Delphinium virescence, dill yellows, Diplotaxis virescence, dogfennel yellows, dogwood stunt, dwarf western aster yellows, eastern aster yellows, Echinacea phyllody, eggplant dwarf, eggplant little leaf, Epilobium phyllody, Erigeron yellows, European aster yellows, false ragweed, Festuca yellows, Gaillardia yellows, Gladiolus virescence, grapevine yellows, grey dogwood stunt, hyacinth yellows, Hydrangea phyllody and virescence, Ipomoea obscura witches' broom, Italian cabbage yellows, Italian lettuce yellows, kale phyllody, larkspur virescence, lazy daisy yellows, lettuce yellows, lilac little leaf, Limonium proliferation, Limonium yellows, Lotus yellows, maize bushy stunt, mallow yellows, marguerite yellows, marigold phyllody, marigold virescence, Maryland aster yellows, Mitsuba witches' broom, monarda yellows, mulberry dwarf, multiplier disease, New England aster yellows, New Jersey aster yellows, oat proliferation, Oenothera virescence, olive witches'-broom, onion phyllody, onion virescence, onion yellows, Papaver virescence, parsley yellows, Paulownia witches' broom, peach red leaf disease, pear proliferation and decline, periwinkle little leaf, periwinkle witches' broom and virescence, periwinkle yellows, Phytoplasma asteris, plantain virescence, Poa stunt, poplar witches' broom, poplar yellows, Portulaca yellows, potato purple top, prickly lettuce yellows, Primula yellows, pumpkin yellows, purple coneflower yellows, Quercus proliferation, ragweed yellows, Ranunculus phyllody, rape phyllody, rape virescence, rose witches'-broom, ryegrass yellows, safflower phyllody, Salix proliferation, sandal spike, Saponaria proliferation, Schizanthus proliferation, severe western aster yellows, soybean purple stem, Spirea stunt, Stellaria yellows, strawberry green petal, strawberry phylloid fruit, strawberry stunting, Symphytum proliferation, Tacaco witches'-broom, Tagetes witches' broom, Thalictrum proliferation, tomato big bud, tomato yellows, turnip virescence, Veronica phyllody, watercress witches'-broom, western aster yellows, wild radish yellows
Worldwide
Widespread
-
2024-11-09
Candidatus Phytoplasma asteris is naturally transmitted by a wide range of leafhopper, Macrosteles fascifrons is reported to be the principal vector. Seed is not a pathway.
Wide host range, primarily herbaceous dicots, though strains infect monocots and woody ornamentals
No
CABICPC, ISFRPLD
Seed is not a known pathway.
CABICPC, ISFRPLD
Aphelenchoides fragariae
nematode
Aphelenchoides olesistus, Aphelenchoides olesistus var. longicollis, Aphelenchoides pseudolesistus
Worldwide, though limited reports in Africa, South America, Canada, Caribbean
Widespread
China
2023-08-21
This nematode has been reported in China
Primarily a pest of strawberry, ferns, ornamentals and flowers of the Liliaceae family. Reported in onion, but not confirmed as a host.
No
APLOFR-1, APLOFR-3, ISFRPLD, NEMAPLEX
Not a host. Onion is not known to be a natural host though listed in APLOFR-1 as an uncommon and unimportant host. No references were found to verify that onion is a host.. Only literature found indicates seed of Anthrium may be a pathway for this nematode (APLOFR-1).
APLOFR-1, APLOFR-3, ISFRPLD, NEMAPLEX
Hunter, Ko, Kunimoto, and Higaki. 1974. A Foliar Disease of Anthurium Seedlings Caused by Aphelenchoides fragariae. Phytopathology 64; 267-268.
Aphelencoides fragariae In: Crop Protection Compendium. Wallingford, UK: CAB International. www.cabi.org/cpc.
Ferris, H. 2019. Nemaplex. www.nemaplex.ucdavis.edu.
Verticillium albo-atrum
fungus
Verticillium albo-atrum var. caespitosum
Verticillium albo-atrum var. tuberosum
Worldwide, primarily in cool temperate climates and in potato producing areas
Widespread, especially in northern states
China, Thailand
2025-09-15
Verticillium albo-atrum is a soilborne fungal pathogen that causes Verticillium wilt in a wide range of host plants, including vegetables, ornamentals, and woody crops. The fungus invades the plant through the roots, colonizes the vascular system, and disrupts water transport. It survives in soil for many years as microsclerotia, making management difficult. The pathogen is primarily spread through infested soil, plant debris, and infected planting material, but seed transmission has been reported (and unverified) in older reports for some crops.
Main: cauliflower. broccoli, lucerne, tomato, potato; Other: brussel sprouts, cucumber
Not a host
VERTAA-2, VERTAA-9, CABI CPC, VERTAA-13
No references found indicating that onion seed is a pathway.
VERTAA-2, VERTAA-9, CABI CPC, VERTAA-13
Anonymous 1960. Index of Plant Diseases in the United States. U.S.D.A. Agric. Handb. 165: 1-531. (94)
Richardson, MJ. 1990. Annotated List of Seedborne Diseases, Fourth Ed. International Seed Testing Association. Zurich, Switzerland
Crop Protection Compendium. Wallingford, UK: CAB International. www.cabi.org/cpc.
Schwartz, H.F. and Mohan, S.K. (Eds) (2008). Compendium of Onion and Garlic Diseases and Pests (Second Edition). American Phytopathological Society (APS Press): St. Paul, Minnesota (USA).
Urocystis cepulae
fungus
Tuburcinia cepulae, Urocystis colchici var. cepulae,
Urocystis magica, Tuburcinia magica, Urocystis allii, Tuburcinia allii, Tuburcinia oblonga, Urocystis oblonga
Africa: Egypt, Gabon, Morocco; Asia: China, India, Iran, Iraq, Israel, Japan, Kazakhstan, Nepal, North Korea, Pakistan, Philippines, South Korea, Taiwan, Tajikistan, Thailand; Europe: Austria, Belgium, Bulgaria, Czechia, Denmark, Finland, France, Germany, Greece, Italy, Malta, Netherlands, Norway, Romania, Russia, Serbia, Slovakia, Sweden, Switzerland, UK; North America: Canada, Cuba, Mexico, Puerto Rico, Saint Lucia, USA; Oceania: Australia, New Zealand; South America: Chile, Peru
CA, MA, MN, NY, OK
China
2025-10-28
Urocystis cepulae is a soil-borne fungus. Vegetative transmission can occur via transplanted infected seedlings. Seed is not a pathway.
Main: onion, leek; Other: garlic
No
UROCCE-3, UROCCE-4
Seed is not known to carry this fungus in trade. Urocystis cepulae teliospores have occasionally been found unattached to seed in seed lots, but seed transmission has not been proven. Seed conditioning should remove any associated fungal spores and physical purity testing should verify removal of any potential contaminate.
Physical purity testing by standard AOSA or ISTA methods
UROCCE-3, UROCCE-4
Physical purity
AOSA/SCST, ISTA
Physical purity to verify that fungal spores are not associated loosely with seed lots
CABI CPC
Most seed treatments applied to seed lots are to protect emerging seedlings from soil borne infections.
Mulder JL, Holliday P, 1971. Urocystis cepulae. Commonwealth Mycological Institute Descriptions of pathogenic fungi and Bacteria No. 298. Wallingford, UK: CAB International.
International Seed Federation Regulated Pest List Database. www.pestlist.worldseed.org., Nyon, Switzerland
AOSA Rules for Seed Testing; www.analyzeseeds.com
International Rules for Seed Testing. International Seed Testing Association; www.seedtest.org
Crop Protection Compendium. Wallingford, UK: CAB International. www.cabi.org/cpc.
Tomato ringspot virus
virus
blackberry (Himalaya) mosaic virus, Euonymus chlorotic ringspot virus, Euonymus ringspot virus, grape yellow vein virus, grapevine yellow vein virus, Nicotiana 13 virus, peach stem pitting virus, prune brown line virus, Prunus stem pitting virus, red currant mosaic virus, tobacco ringspot virus 2, tomato ringspot nepovirus, ToRSV, winter peach mosaic virus
Africa: Egypt, Nigeria, Togo; Asia: China, India, Iran, Japan, Jodan, Lebanon, Oman, Pakistan, South Korea, Taiwan, Turkey; Europe: Belarus, Croatia, France, Netherlands, Poland, Russia, Slovakia, Spain, UK; North America: Canada, Puerto Rico, USA; Oceania: Fiji, New Zealand; South America: Brazil, Chile, Colombia, Peru, Venezuela.
Widespread
Korea, Mexico, Thailand
2022-11-07
Natural spread is confined to areas where there are moderate to high populations of nematode vectors belonging to the genus Xiphinema. Requires the nematode to spread. Seed transmission only shown in strawberry and raspberry in nature.
Wide host range, primarily ornamentals and fruit trees and berries. Vegetable crops infected are listed below. Not known to infect grains and grasses
No
TORSV0-2, TORSV0-4, TORSV0-5
No references found indicting onion is infected by this virus
TORSV0-2, TORSV0-4, TORSV0-5
Brunt, AA, Crabtree, K., Dallwitz, MJ, Gibbs, AJ, Watson, L. and Zurcher, EJ. (eds.). Plant Viruses Online: Descriptions and Lists from the VIDE Database, Version: 16th 1997. http://bio-mirror.im.ac.cn/mirrors/pvo/vide/refs.htm
International Seed Federation Pest List Database. http://www.worldseed.org Nyon Switzerland
Richardson, MJ, 1990. An Annotated List of Seed-borne Diseases. International Seed Testing Association, Zurich Switzerland
Tobacco mosaic virus
virus
TMV U1, type, Vulgare or Common strain
tobacco mosaic tobamovirus,
VMT (Virus mosaique de tabac)
Worldwide
Widespread
Mexico
2023-08-21
Broad host range. Cultivated species listed below.
No
TMV000-1, TMV000-11
No references found indicating that A. cepa is a host for TMV.
TMV000-1, TMV000-11
Tomato spotted wilt virus
virus
Tomato spotted wilt tospovirus, Tomato spotted wilt virus group
Worldwide
Widespread
2023-08-21
Seed is not a pathway for Tospoviruses, including Tomato spotted wilt virus
Wide host range. Over 800 plant species are known hosts. Primarily ornamentals,flowers. No evidence that small grains or corn are hosts.
No
TSWV00-1, TSWV00-2
Seed is not a pathway for Tospoviruses, including Tomato spotted wilt virus. No evidence that onion is a host.
TSWV00-1, TSWV00-2
Botryotinia porri
fungus
Botrytis porri, Sclerotinia porri
Asia: China, Iran, Japan; Europe: Finland, Germany, Hungary, Norway, UK; North America: Canada, USA; Oceania: Australia, New Zealand; South America: Chile, Venezuela.
CA, NV, OR, WA
Brazil, Mexico
2025-08-01
Botryotinia porri primarily spreads through wind- or rain-dispersed spores and survives in the soil, thriving in cool, moist climates. It may move via infected garlic bulbs or leeks, but seedborne transmission is unlikely. While it could spread to new areas, its impact is moderate, and establishment in tropical regions is unlikely.
Main: onion, leek; Other: garlic
uncertain
BOTTPO-2, BOTTPO-3, BOTTPO-4, CABI CPC
Only one report of seed being a pathway for B. porri in onion (BOTTPO-2). No other references were found indicating onion seed as a pathway.
BOTTPO-2, BOTTPO-3, BOTTPO-4, CABI CPC
Blotter incubation
BOTTPO-2
This test has not been validated or standardized.
Cultural
CABI CPC
Good hygiene will prevent the persistence of sclerotia or infected crop debris in the soil. Agricultural practices that would create cool moist conditions in the upper layers of the soil should be avoided, in particular in relation to irrigation.
du Toit LJ, Derie ML, Hsiang T, Pelter GQ, 2002. Botrytis porri in onion seed crops and onion seed. Plant Disease, 86:1178.
du Toit LJ, Derie ML, and Pelter, GQ 2004, Prevalence of Botrytis spp. in Onion Seed Crops in the Columbia Basin of Washington.Plant Disease 88: 1061-1068
International Seed Federation Regulated Pest List Database. www.pestlist.worldseed.org. Nyon, switzerland
Crop Protection Compendium. Wallingford, UK: CAB International. www.cabi.org/cpc.
Pleospora herbarum
fungus
Too many to list, most commonly used names include Alternaria putrefaciens, Clasterosporium putrefaciens, Sporidesmium putrefaciens, Stemphyllium botryosum, Stemphylium herbarum.
Worldwide
Widespread
2023-08-21
Primarily a post harvest pathogen
Wide host range
No
PLEOHE-2, PLEOHE-4
Pathway not proven. Some references indicate an association of Stemphylium botryosum spores with seed, however, no references found to indicate that seed is a proven pathway in onion.
PLEOHE-2, PLEOHE-4
Stemphylium vesicarium
fungus
Pleospora alli, Helminthosporium vesicarium, Macrosporium alliorum, Mystrosporium alliorum, Macrosporium parasiticum, Stemphylium parasiticum
Worldwide
AZ, CA, FL, MI, MN, NM, NY, TX, WA
-
2024-10-22
Ascospores (P. allii) and conidia (S. vesicarium) are mainly wind-blown or water-dispersed.
Main: onion, garlic, asparagus, soybean, alfalfa, tomato; Other: leek, sunflower, lettuce, radish.
Yes
PLEOAL-10, PLEOAL-8, CABICPC
Seed as a pathway is documented and accepted. It is more severe under warm and moist conditions.
PLEOAL-10, PLEOAL-8, CABICPC
Agar Incubation
PLEOAL-10, PLEOAL-12, NSHSUSDA
This test has not been validated or standardized
Cultural, Chemical
PLEOAL-10, PLEOAL-12
Early detection is possible by trapping air-born conidia using spore traps. Remove or bury plant debris to reduce primary inoculum. Allow adequate airflow, avoid long periods of leaf wetness, reduce plant density, and include good drainage. Seed treatments effective.
International Seed Federation Regulated Pest List Database. www.pestlist.worldseed.org. Nyon, switzerland
Jakhar SS, Suhag LS, Duhan JC, 1994. Prevalence and incidence of Stemphylium blight of onion (Allium cepa L.) and its management through cultural practices. Crop Research (Hisar), 8(3):562-564 (See CABI)
Aveling, T.A.S., Snyman, H.G. and Naude, S.P. (1993). Evaluation of seed treatments for reducing Alternaria porri and Stemphylium vesicarium on onion seed. Plant Disease, 77, 1009-1011.
Iris yellow spot virus
virus
Iris yellow spot tospovirus
Worldwide
AZ, CA, CO, GA, HI, ID, MI, NV, NM, NY, OR, PA, TX, UT, WA
Korea
2025-08-04
Iris Yellow spot virus is spread by thrips, infected seedlings, and infected bulbs. Seed is not known to be a pathway for any host.
Main: onion, shallot, leek, chive, Iris; Other: garlic, lily, cowpea
No
CABI CPC, EPPO
Seed is not known to be a pathway. Iris yellow spot virus is not known to be a seed transmitted virus.
CABI CPC, EPPO
Xanthomonas axonopodis pv. allii
bacterium
Xanthomonas campestris pv. alli
Africa: Mauritius, Reunion, South Africa; Asia: Japan, Myanmar; North America: Barbados, Cuba, Saint Kitts and Nevis, USA; South America: Brazil, Venezuela.
CA, CO, GA, HI, TX
Korea
2025-07-14
Xanthomonas axonopodis pv. allii causes leaf blight in Allium species. It is primarily seed-transmitted but can also spread through infected transplants, crop debris, and water splash from rain or irrigation.
Main: onion, shallot, leek, garlic
Yes
XANTAA-4, CABI CPC, ISF RPLD, EPPO, XANTAA-6
Seed is known to be a pathway.
XANTAA-4, CABI CPC, ISF RPLD, EPPO, XANTAA-6
Seed wash/liquid plating, Bio-PCR
XANTAA-4, XANTAA-5, ISF RPLD
Selective media and a BIO-PCR methods described. No validated or commercial seed assay available. PCR is an indirect way of testing (no isolation of the pathogen) and does not distinguish between viable and non-viable pathogen.
cultural
ISF RPLD, EPPO
No seed treatments known to be effective. Control of Xanthomonas axonopodis pv. allii relies on an integrated approach: using healthy seeds and bulbs, destroying volunteer onions and plant debris, implementing crop rotations, and applying chemical controls. These measures are most effective when used in combination.
Roumagnac, P., Gagnevin, L., and Pruvost, O. 2000. Detection of Xanthomonas sp., the causal agent of onion bacterial blight, in onion seeds using a newly developed semi-selective isolation medium. Eur. J. Plant Pathol. 106:867-877.
Crop Protection Compendium. Wallingford, UK: CAB International. www.cabi.org/cpc.
International Seed Federation Regulated Pest List Database. pestlist.worldseed.org Nyon Switzerland
OEPP/EPPO Global Database - European and Mediterranean Plant Protection Organization
Gagnevin L, Bolot S, Gordon JL, Pruvost O, Vernière C, Robène I, Arlat M, Noël LD, Carrère S, Jacques MA, Koebnik R. Draft Genome Sequence of Xanthomonas axonopodis pv. allii Strain CFBP 6369. Genome Announc. 2014 Jul 31;2(4):e00727-14. doi: 10.1128/genomeA.00727-14. PMID: 25081256; PMCID: PMC4118059.
Robene-Soustrade, I., Legrand, D., Gagnevin, L., Chiroleu, F., Laurent, A. and Pruvost, O. 2010. Multiplex nested PCR for detection of Xanthomonas axonopodis pv. allii from onion seeds. Applied and Environmental Microbiology, 76:2697-2703.
Fusarium redolens
fungus
Fusarium oxysporum var. redolens, Fusarium redolens var. solani, Fusarium solani var. redolens
Africa: Algeria, Tunisia; Asia: China, Iran, Japan, Pakistan, Turkey; Europe: Czechia, Finland, Netherlands, Poland, Sweden, UK; North America: Canada, USA,; Oceania: New Zealand.
MT, ND.
Korea
2024-09-04
No references found indicating seed is a pathway. Fusarium redolens is soil-borne.
An economic pathogen of carnation. Though reported on other vegetable and grain crops, it is not considered an economic pathogen of many hosts or its economic importance is not known.
No
CABICPC
No references found indicating seed is a pathway. Only one reference found indicating onion may be a host in Finland. Not considered an economic pathogen of onion.
CABICPC
Phytophthora porri
fungus
Africa: South Africa, Asia: Japan, Europe: widespread, Canada, Australia
None. The report from WI, USA is actually Phytophthora brassicae (USDA FD).
2024-05-04
Seed is not known to be a pathway. All reports of post harvest diseases in brassica probably due to Phytophthora brassiceae and not Phytophthora porri (Farr and Rossman, 2018). Lettuce was listed as a possible host, but no data found to confirm.
onion, leek. Reported as a post harvest disease in carrot.
No
PHYTPO-2, CABICPC
Seed is not known to be a pathway for Phytophthora porri.
PHYTPO-2, CABICPC
Setophoma terrestris
fungus
Pyrenochaeta terrestris, Phoma terrestris
Africa: Senegal; Asia: India, Israel; Europe: Greece, Netherlands, Poland; North America: Mexico, USA; Oceania: Australia; South America: Argentina, Venezuela.
DE, IA, MD, VA.
Korea
2024-09-24
Ubiquitous soil fungus. Often a secondary invader of plant roots when weakened by other pathogens.
Wide host range, though only producing symptoms and disease on onion, corn and rice.
No
PYRETE-4, ISFRPLD, PYRETE-5
Seed is not known to be a pathway.
PYRETE-4, ISFRPLD, PYRETE-5
Sumner, DR. 2008 Pink Root. In, Compendium of Onion and Garlic Diseases and Pests, Second Edition. Eds. Schwartz, HF and Mohan, SK., American Phytopathological Society, St. Paul, MN, USA
Levic, J., Petrovic, T., Stankovic, S., & Ivanovic, D. (2013). The incidence of Pyrenochaeta terrestris in root of different plant species in Serbia. Zbornik Matice Srpske Za Prirodne Nauke, 2013(125), 21–30.
Cercospora duddiae
fungus
-
Asia: India; North America: Barbados, Jamaica.
Not known to occur
Korea
2024-11-26
Transmission is by air-borne or water-splash dispersed conidia, and by transportation with onion parts.
onion, garlic
Uncertain
CERCDU-2, CERCDU-3, CABICPC, ISFRPLD, CERCDU-4
Only one reference noted from 1960 indicating seed may be a pathway; however that document was not found, nor any new references since. Infects primarily mature plants (CERCDU-3)
CERCDU-2, CERCDU-3, CABICPC, ISFRPLD, CERCDU-4
Farr, D.F. and Rossman, A.Y. Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. 2019, http://nt.ars-grin.gov/fungaldatabases/
Mayur DA. and Borse KN, 2015. Common Fungal Leaf spot diseases of Allium cepa L. and Allium sativum L.
Crop from Maharashtra state, India. Int. Res. J. Biological Sci. 4:34-37
Little, S. (1987). Cercospora duddiae.[Descriptions of Fungi and Bacteria]. Descriptions of Fungi and Bacteria, (92), Sheet-920.
Tobacco rattle virus
virus
Aster ringspot virus, belladonna mosaic virus, paeony mosaic virus, paeony ringspot virus, peony mosaic virus, peony ringspot virus, potato corky ringspot virus, potato stem mottle virus, ratel virus, spinach yellow mottle virus, Tabakmauche Virus, Tabakstreifen und Kra, tobacco rattle tobravirus, tulip white streak virus
Worldwide
AK, CA, CO, FL, ID, IL, IN, MA, MI, MN, NE, NC, ND, OH, OR, PA, UT, WA, WI
Korea
2024-09-08
Tobacco Rattle Virus is soil-borne and transmitted between plants by the nematode species Trichodorus and Paratrichodorus. Seed is only known to be a pathway in some weed species.
TRV occurs on numerous crops in many countries and has been detected on over 100 mono- and dicotyledonous plant species.
Pathway not proven
TRV000-6, CABICPC
One reference found indicating seed transmission via mechanical inoculation. There were no other references found indicating seed is a pathway for tobacco rattle virus in nature.
TRV000-6, CABICPC
Pseudomonas syringae pv. syringae
bacterium
Many
Worldwide
Widespread
Thailand, China, Korea
2022-12-01
Seed is known to be a pathway on several crops. Thailand lists this pathogen as prohibited on corn. China lists this pathogen (Pseudomonas oryzicola) as prohibited on rice.
Wide host range. Important vegetable and agronomic crops listed below.
Not a host
PSDMSY-2
No references found indicating onion is a host for this bacterium.
PSDMSY-2
International Seed Federation Regulated Pest List Database. pestlist.worldseed.org Nyon, Switzerland
Pythium vexans
fungus
Pythium complectens, Phytopythium vexans, Pythium allantocladon, Pythium ascophallon, Pythium piperinum, Ovatisporangium vexans, Pythium euthyphyphon, Pythium polycladon
Africa, Asia, Europe, Guatemala, Caribbean, Fiji, Papua New Guinea, Samoa, Solomon Islands, Argentina, Brazil, Venezuela, Chile, South Korea, New Zealand, Canada
HI, OK, CA, NC, MD, VA, DE, PA, NJ, WA, TN, LA, WI, IA
Korea
2023-08-21
Primarily affecting seedlings and roots and is transmitted mainly through infested soil. Seed is not known to be a pathway for any host. Zoospores of this fungus can swim in open water for a short distance. This pathogen has been reported in S. Korea. Korea lists this pathogen as Phytopythium vexans
Wide host range
No
PYTHVE-1, PYTHVE-3, PYTHVE-4
Seed is not known to be a pathway for any host.
PYTHVE-1, PYTHVE-3, PYTHVE-4
Pythium vexans In: Crop Protection Compendium. Wallingford, UK: CAB International. www.cabi.org/cpc.
Richardson MJ, 1990. An Annotated List of Seed-borne Disease. International Seed Testing Association, Zurich, Switzerland
International Seed Federation Regulated Pest List Database. www.pestlist.worldseed.org. Nyon, switzerland
Pratylenchus brachyurus
nematode
Anguillulina brachyura, Pratylenchus leiocephalus, Pratylenchus pratensis, Pratylenchus steineri, Tylenchus brachyurus
Worldwide, primarily in tropical and subtropical regions.
AL, AR, CA, FL, GA, HI, KY, LA, MD, MS, NC, OK, SC, TN, TX, VA
Korea
2025-08-13
Pratylenchus brachyurus is a root-lesion nematode that reproduces mainly by mitotic parthenogenesis. It spends its entire life cycle inside plant roots or in surrounding soil, feeding and moving within root tissues. Eggs overwinter in roots or soil, hatching in spring to resume infection. Seed is not known to be a pathway.
Wide host range. Main hosts of economic importance: pineapple, potatoes, peanuts, cotton, tobacco, peaches, cereals, coffee, soybean.
Not a host
CABI CPC, PRATBR-4, PRATBR-5, PRATBR-6, PRATBR-7
Though listed as a possible host, no other reference lists onion as a host. Seed is not known to be a pathway for this nematode in any of its hosts.
CABI CPC, PRATBR-4, PRATBR-5, PRATBR-6, PRATBR-7
Crop Protection Compendium. Wallingford, UK: CAB International. www.cabi.org/cpc.
Nemaplex.UCDavis.edu; Revision Date: 16-December-2024; Accessed 13-August-2025
Nomura, R. B. G., Lopes-Caitar, V. S., Hishinuma-Silva, S. M., Machado, A. C. Z., Meyer, M. C., & Marcelino-Guimarães, F. C. (2024). Pratylenchus brachyurus: status and perspectives in Brazilian agriculture. Tropical Plant Pathology, 49(5), 573-589.
Agrios, G. N. 2005. Plant Pathology, 5th Edition. Elsevier Academic Press. 922 pp
Chitambar, J. J., Westerdahl, B. B., and Subbotin, S. A. 2018. Plant Parasitic Nematodes in California Agriculture. In Subbotin, S., Chitambar J., (eds) Plant Parasitic Nematodes in Sustainable Agriculture of North America. Sustainability in Plant and Crop Protection. Springer, Cham.
Phytophthora cinnamomi
fungus
-
Worldwide
Widespread
Korea
2024-12-20
Phytophthora cinnamomi is dispersed by soil-splash, wind-blown, plant debris, and water movement. Seed is not known to be a pathway.
Wide host range, primary trees and woody ornamentals
Not a host
Though the USDA Fungal Database list onion as a potential host, no references were found confirming onion is a host.
Cladosporium cladosporioides
fungus
Cladosporium graminum, Cladosporium herbarum, Mycosphaerella schoenoprasi, Mycosphaerella tulasnei, Mycosphaerella tassiana, Penicillium cladosporioides, Hormodendrum cladosporioides, Monilia humicola
Africa: Egypt, South Africa; Asia: Bangladesh, China, India, Iran, Israel, Oman, Saudi Arabia, South Korea, Syria; Europe: France, Hungary, Italy; North America: USA; South America: Argentina, Brazil
IA, OR
Korea
2025-10-07
This pathogen is considered primarily a post harvest pathogen that does not cause disease in most of it's hosts (CLADCL-1). C. cladosporioides spreads primarily by wind, rain splash, or contaminated surfaces. It can also persist on plant debris, some seeds, and stored produce, serving as inoculum for new infections. The fungus thrives in cool, moist environments and is especially common in greenhouses, storage areas, and outdoor crops during humid seasons.
Wide host range
No
CABI CPC, CLADCL-12
No references found indicating onion seed is a pathway.
CABI CPC, CLADCL-12
Alternaria alternata
fungus
Alternaria alternata f.sp. fragariae
Alternaria alternata f.sp. lycopersici
Alternaria fasciculata
Alternaria tenuis
Worldwide
AL, CA, FL, GA, IL, IA, LA, MI, MS, NY, OR, PA, SD, TN, TX
Korea
2025-09-08
Alternaria alternata is a widespread fungus that can persist in soil and crop debris for many years, enabling it to infect plants across successive growing seasons. Its spores are dispersed by air, wind, water splash, irrigation, and contact with contaminated plant material. Numerous studies have demonstrated its transmission under experimental conditions, and it has been shown to be seed-transmitted in a few crops within the Malvaceae family.
Main: allium, pepper; Other: watermelon, sunflower, sorghum, spinach, marigold, many fruits and trees
No
ALTEAL-4, CABI CPC, ALTEAL-39
No references found indicating seed is a pathway. Onion has been reported a host of the pathogen. This fungus is ubiquitous and found on many plant species.
ALTEAL-4, CABI CPC, ALTEAL-39
Richardson MJ, 1990. An Annotated List of Seed-borne Disease. International Seed Testing Association, Zurich, Switzerland
Crop Protection Compendium. Wallingford, UK: CAB International. www.cabi.org/cpc.
Reyes-Tena, A., Montoya-Martínez, A. C., Fernández-Pavía, S. P., Santillán-Mendoza, R., Jiménez-Villegas, A., Pineda-Vaca, D., & Rodríguez-Alvarado, G. (2024). Onion leaf blight caused by Alternaria alternata sensu lato and Stemphylium vesicarium in Michoacán, México. Canadian Journal of Plant Pathology, 46(2), 79-88.
Pantoea ananatis
bacterium
Bacillus ananas, Bacterium ananas, Chromobacterium ananas, Erwinia ananas pv. uredovora, Erwinia ananatis,Erwinia herbicola var. ananas, Erwinia urediniolytica,Erwinia uredovora, Pantoea ananas pv. ananas, Pantoea ananas pv. uredovora, Pantoea ananatis pv. ananatis,Pantoea ananatis pv. uredovora, Pectobacterium ananas, Pectobacterium ananatis pv. ananatis, Xanthomonas uredovora
Africa, Asia, Belgium, Italy, Russia, Poland, Spain, Nova Scotia, Mexico, Haiti, Puerto Rico, Guatemala, Australia, Argentina, Ecuador, Brazil, Guyana, Uruguay, Venezuela
CA, CO, FL, GA, MI, TX, NY
Chile
2023-07-28
Probably ubiquitous, causes post harvest rots in vegetables such as tomato, cantaloupe and some berries. Causes diseases in the field in the hosts listed below. Reported in host range studies on other Poaceae species. Most common in warm, wet climatic conditions.
onion, corn, rice, sudangrass, pineapple.
Yes
CABICPC, ISFRPLD, ERWIAN-1, ERWIAN-2, ERWIAN-3, ERWIAN-4, ERWIAN-6
Contamination of seed by this bacteria is well documented.
CABICPC, ISFRPLD, ERWIAN-1, ERWIAN-2, ERWIAN-3, ERWIAN-4, ERWIAN-6
PCR, Plating on semi-selective media
ISFRPLD, ERWIAN-4, ERWIAN-1
Use of both methods suggested. These methods have not been standardized or validated.
CABICPC
Cultural practices to reduce this pathogen in weeds and thrips are suggested
Walcott, RR, et.al. 2002. Natural infestation of onion seed by Pantoea ananatis, causal agent of center rot. Plant Disease, 86, 106-111.
Goszczynska, T., et.al. 2006. Isolation and identification of Pantoea ananatis from onion seed in South Africa. Seed Science and Technology 34: 655-668
Gent, DH and Schwartz, HF. 2008. Center Rot. In, Compendium of Onion and Garlic Diseases and Pests, Second Edition. Eds. Howard F. Schwartz and S. Krishna Mohan. American Phytopathological Society, St. Paul, MN, USA
Goszczynska, T, Venter, SN, Coutinho, TA. 2006. PA 20, a semi-selective medium for isolation and enumeration of Pantoea ananatis. Journ. of Microbiological Methods 64: 225-231
Khanal, M., Bhatta, B., & Malla, S. (2023). Isolation and characterization of bacteria associated with onion and first report of onion diseases caused by five bacterial pathogens in texas, u.s.a. Plant Disease, 107(6), 1721–1729
Shallot yellow stripe virus
virus
Welsh onion yellow stripe virus
Asia: China, Vietnam.
Not known to occur
Korea
2024-11-24
Aphid transmitted potyvirus. Potyviruses are not known to be seed transmitted.
shallot, onion
No
No references found indicating seed is a pathway.
Erwinia rhapontici
bacteria
Aplanobacter rhapontici, Bacillus rhapontici, Bacterium rhapontici, Erwinia carotovora var. rhapontici, Pectobacterium rhapontici, Phytomonas rhapontici, Pseudobacterium rhapontici,Xanthomonas rhapontici
Asia, Europe, Canada, Mexico, New Zealand
Western and Midwest states
Brazil
2023-04-20
Brazil lists this as Pectobacterium rhapontici.
Primarily rhubarb and wheat. Reported on a few vegetables.
No
CABI CPC, ISF RPLD
This bacteria is a wound pathogen known to occur on onions. No references found indicating seed as a pathway in onion. Seed can be a pathway in peas and bean.
CABI CPC, ISF RPLD
Ditylenchus destructor
nematode
-
Africa: Nigeria, South Africa; Asia: Azerbaijan, China, Iran, Japan, Pakistan, Saudi Arabia, South Korea, Syria, Tajikistan, Turkey, Uzbekistan; Europe: Albania, Austria, Belarus, Bulgaria, Czechia, Estonia, France, Greece, Hungary, Ireland, Jersey, Latvia, Luxemburg, Moldova, Netherlands, Norway, Poland, Romania, Russia, Slovakia, Sweden, Switzerland, Ukraine, UK; North America: Canada, USA; Oceania: New Zealand.
CA, HI, ID, OR, SC, WA, WI
-
2024-09-26
Ditylenchus destructor is spread through seed potatoes. It is also spread on containers, packaging, and soil. True seed is not know to be a pathway.
Extensive host range. Main: ornamental bulbs, sweet potato, onion, garlic, groundnut, beet, sugarbeet, pepper, cucumber, pumpkin, carrot, soybean, tomato, potato, clover, wheat, corn
No
CABICPC, ISFRPLD, EPPO, DITYDE-1
Seed is not a known pathway.
CABICPC, ISFRPLD, EPPO, DITYDE-1
Stromatinia cepivora
fungus
Sclerotium cepivorum, Stromatinia cepivorum
Worldwide
CA, KY, LA, NJ, OH, OR, PA, TX, VA
-
2025-10-23
Stromatinia cepivora is a soil-borne fungus that causes white rot in onions, garlic, and other Allium crops. It produces small black sclerotia that can survive in soil for decades and germinate only in response to Allium root compounds. It spreads through contaminated soil, bulbs, and equipment, thriving in cool, moist conditions.
Main: onion, shallot, leek, garlic, chives
No
CABI CPC, SCLOCE-1, SCLOCE-2, SCLOCE-3
Onion seed is not a known pathway.
CABI CPC, SCLOCE-1, SCLOCE-2, SCLOCE-3
Crop Protection Compendium. Wallingford, UK: CAB International. www.cabi.org/cpc.
Vargas Baquero, C. D., & Cotes, A. M. (2023). Microbial consortia as an option for biocontrol of Stromatinia cepivora. Canadian Journal of Plant Pathology, 46(1), 1–10.
Coley-Smith, J. R. (1990). White rot disease of AIlium: problems of soil-borne diseases in microcosm. Plant Pathology, 39(2).
Osman, H. E. M., Nehela, Y., Elzaawely, A. A., El-Morsy, M. H., & El-Nagar, A. (2023). Two Bacterial Bioagents Boost Onion Response to Stromatinia cepivora and Promote Growth and Yield via Enhancing the Antioxidant Defense System and Auxin Production. Horticulturae, 9(7), 780.
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