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Photo Gallery of Vegetable Problems – Onions/Allium


General Onion/Allium Disease and Pest Management

Onion ipmPIPE Diagnostic Pocket Series Onion Disease Risk Assessment

Diseases

Bacterial soft rot

Basal rot

Black mold

Downy mildew

Diseases of stored garlic

Fusarium basal rot

Iris yellow spot

Neck rot

Pink root

Rhizoctonia stunting

Root rot

Rust

Onion Smut

White rot

Insect/Mite Pests

Bulb mites/eriophyid mites

Seedcorn maggot

Two-spotted spider mite

Thrips

Wireworm

Weeds

Dodder

Yellow nutsedge

Abiotic Problems

Basal plate splitting, basal plate blow-out

General Onion/Allium Disease and Pest Management

Onion Disease Guide – A Practical Guide for Seedsmen, Growers and Agricultural Advisors. Published by Seminis Vegetable Seeds, Inc.’s Plant Health Department.

Pest Management Strategic Plan for Dry Bulb Storage Onions in the United States
SCRI Project Updates Talks and Publications, Allium Net.
Onion ipmPIPE Brochure

Onion ipmPIPE Diagnostic Pocket Series

Soil-Borne Diseases
Storage Fungal Diseases
Storm Damaged Onions
Virus Diseases

Onion Disease Risk Assessment

Thrips & Iris yellow spot virus (IYSV) Forecast
Bacterial Disease Forecasts
Fungal Disease Forecasts

(Click on photos to enlarge)

Diseases

Disease: Bacterial soft rot
Pathogen: Bacterial species

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Photo Source: G.Q. Pelter

On-Line Resources:

Bacterial Diseases, Onion ipmPIPE Diagnostic Pocket Series


Disease: Basal rot
Pathogen: Botytis allii and Fusarium roseum

Basal rot on onion.
Basal rot on onion.
Photo Source: G.Q. Pelter

On-Line Resources:

Onions, Garlic: Basal rot, Washington State University Hortsense

Storage Fungal Diseases, Onion ipmPIPE Diagnostic Pocket Series


Disease: Black mold
Pathogen: Aspergillus niger

Photo Source: G.Q. Pelter
Photo Source: Lindsey du Toit, Washington State University

On-Line Resources:

Pacific Northwest Plant Disease Management Handbook: Onion (Allium cepa) – Black Mold

Storage Fungal Diseases, Onion ipmPIPE Diagnostic Pocket Series

Disease: Diseases of storage garlic

See: Diseases of Storage Garlic (Oregon State University)


Disease: Downy mildew
Pathogen: Peronospora d

Photo Source: Lindsey du Toit, Washington State University

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On-Line Resources:

Pacific Northwest Plant Disease Management Handbook: Onion (Allium cepa) – Downy Mildew

Foliar Fungal Diseases, Onion impPIPE Diagnostic Pocket Series

Onions, Garlic: Downy mildew, Washington State University Hortsense


Disease: Fusarium basal rot
Pathogen: Fusarium species

Photo Source: G.Q. Pelter

On-Line Resources:

Pacific Northwest Plant Disease Management Handbook: Onion (Allium cepa) – Fusarium Basal Rot

Storage Fungal Diseases, Onion impPIPE Diagnostic Pocket Series


Disease: Iris yellow spot (IYS)
Latin binomial: Iris yellow spot virus (IYSV)
Host Crops: Primarily Allium spp., particularly bulb onion (A. cepa), but a range of common weed species in onion crops has been identified as potential symptomatic and asymptomatic hosts.

Photo Source: Lindsey du Toit, Washington State University Photo Source: Fred Crowe, Oregon State University Professor Emeritus

On-Line Resources:

Iris yellow spot virus: An Emerging Threat to Onion Bulb and Seed Production

Susceptibility of storage onion cultivars to iris yellow spot in the Columbia Basin of Washington, 2004, L.J du Toit, Washington State University and G.Q. Pelter, Washington State University

Pacific Northwest Plant Disease Management Handbook: Onion (Allium cepa) – Iris Yellow Spot


Disease: Neck rot
Pathogen: Botrytis allii and Botrytis aclada are the two primary species that cause neck rot of onion, although as many as six species of Botrytis can infect various Allium spp.
Host Crops: Onion (Allium cepa) and other Allium spp.

Photos of neck rot of onion
Photo Source: Jordan Eggers, Oregon State University
Photos of neck rot of onion
Photo Source: Jordan Eggers, Oregon State University Photo Source: Lindsey du Toit, Washington State University

On-Line Resources:

Pacific Northwest Plant Disease Management Handbook: Onion (Allium cepa) – Neck Rot

Important New York Vegetable Diseases: Onion Neck Rot, Vegetable MD Online, Cornell University

Botrytis Neck Rot of Onion, EB1359, Washington State University Extension

Onion neck rot, The Royal Horticultural Society

Detection and Identification of Botrytis Species Associated with Neck Rot, Scape Blight, and Umbel Blight of Onion, Plant Management Network

A Real-Time, Quantitative PCR Seed Assay for Botrytis spp. that Cause Neck Rot of Onion, Plant Disease, The American Phytopathological Society


Disease: Root rot
Pathogen: Trichodorus and Pythium

Photo Source: G.Q. Pelter

On-Line Resources:

Disease: Pink root
Pathogen: Phoma terrestris (Pyrenochaeta terrestris)
Host Crops: Primarily onion, but some strains of the fungus are pathogenic on barley, cantaloupe, carrot, cauliflower, cucumber, eggplant, pea, corn, millet, muskmelon, oat, pepper, ryegrass, sorghum, soybean, spinach, squash, sweet corn, tomato, and wheat.

Photo Source: Carrie Wohleb, Washington State University Photo Source: Lindsey du Toit, Washington State University

On-Line Resources:

Pacific Northwest Plant Disease Management Handbook: Onion (Allium cepa) – Pint Root

Soil-Borne Diseases of Onion, Colorado State University Extension

UC Pest Management Guidelines: Onion and Garlic Pink Root, UC IPM Online, University of California


Disease: Rhizoctonia stunting (also known as ‘Mallee’ in Australia after the Mallee region of South Australia, where the disease was first documented in that country)
Causal agent (Latin binomial): Rhizoctonia spp., particularly Rhizoctonia solani (various anastomosis groups, including AG 8). The fungi colonize the roots of winter cover crops planted preceding onion bulb crops. The cover crop is killed with a herbicide application in spring, around the time that onion seed is planted, to provide a physical barrier to protect emerging onion seedlings from wind- and sandblasting on the sandy soils typical of many fields in the Columbia Basin of central Washington and northcentral Oregon. Herbicide is applied to the cover crop to prevent the cover crop from competing with the onion crop. However, this enables Rhizoctonia spp. to colonize the dying roots and crown tissue of the cover crop, building up inoculum that can then colonize onion seedlings.
Host Crops: Onion, pea, cereals, other crops.

Photo Source: Tim Paulitz, USDA ARS, Pullman, WA. Photo Source: Lindsey du Toit, Washington State University

On-Line Resources:

Stunting of Onion in the Columbia Basin of Oregon and Washington Caused by Rhizoctonia spp. Plant Disease 97:1626–1635.

Effect of timing of glyphosate application to a winter wheat cover crop on stunting of spring-sown onions caused by Rhizoctonia spp. in the Columbia Basin of Washington, 2012, Plant Disease Management Reports 7:V046, 2013.

Efficacy of fungicides to manage onion stunting caused by Rhizoctonia spp. in the Columbia Basin of Oergon and Washington, 2011–2012, Plant Disease Management Reports 7:V047, 2013.

Yield responses of three onion cultivars to stunting caused by Rhizoctonia spp. in the Columbia Basin of Oregon and Washington, 2012. Plant Disease Management Reports 7:V048, 2013.

Rhizoctonia Seedling Blight of Onion and Pea Crops in the Columbia Basin, WSU 2011 Onion Field Day report, Soap Lake, WA, 26 Aug. 2011

Rhizoctonia Seedling Blight of Onion Crops in the Columbia Basin, WSU 2012 Onion Field Day report, Connell, WA, 30 Aug. 2012

Onion Stunting Caused by Rhizoctonia: Management and Economic Importance in the Columbia Basin of Oregon and Washington, Proceedings article from 2012 National Allium Research Conference, Las Cruces, NM, 12–14 Dec. 2012


Disease: Rust
Pathogen: Puccinia allii (= Puccinia porri)
Host Crops: Onion and garlic.

Photo Source: Seth Lewis, WSU NWREC Vegetable Pathology program Photo Source: Johnny Stark, WSU Puyallup PIDL

On-Line Resources:

Pacific Northwest Plant Disease Management Handbook: Onion (Allium cepa) – Rust

Diseases of onion and garlic ( Allium sepa and Allium sativa ) in Arizona: Garlic Rust, University of Arizona

UC Pest Management Guidelines: Onion and Garlic Rust, UC IPM Online, University of California

Prediction of Disease Infection of Welsh Onions by Rust Fungus Based on Temperature and Wetness Duration, IEEEXplore


Disease: Onion Smut
Pathogen: Urocystis colchici (= Urocystis cepulae)

Photo Source: D.A. Inglis Photo Source: Lindsey du Toit

On-Line Resources:

Onion Smut, Identification & Management of Emerging Vegetable Problems in the Pacific Northwest. Pacific Northwest Vegetable Extension Group.

Pacific Northwest Plant Disease Management Handbook: Onion (Allium cepa) – Smut

Efficacy Testing of Onion Seed Treatments in the Greenhouse and Field. Acta Hort. 631 in 2004 by McDonald et al.

Onion disorder: Smut. University of Wisconsin extension bulletin


Disease: White rot
Pathogen: Sclerotinia cepivorum
Host plants: Garlic, onion, and other Allium spp.

Photo Source: G.Q. Pelter
Photo Source: Lindsey du Toit, Washington State University.

On-Line Resources:

Pacific Northwest Plant Disease Management Handbook: Onion (Allium cepa) – White Rot

Onions, Garlic: White rot, Washington State University Hortsense

Soil-Borne Diseases, Onion ipmPIPE Diagnostic Pocket Series


Insect/Mite Pests

Common name: Bulb mites/eriophyid mites

Latin binomial: Aceria tulipae, an eriophyid mite, appears most commonly associated with damage to garlic in storage. Various bulb and eriophyid mites can feed on garlic cloves and bulbs of other Allium spp.

Host crops: Various Allium spp. as well as other plants or decaying organic matter. Severe infestations can cause desiccation of bulbs, and mites can vector garlic-rotting fungi.

Damage to garlic cloves caused by eriophyid mite feeding.
Photo Source: Lindsey du Toit, Washington State University

Online Resources:

http://www.science.oregonstate.edu/bpp/Plant_Clinic/Garlic/eriophyids.htm

http://ecoport.org/ep?SearchType=pdb&PdbID=16129

Moth balls (the kind used to keep moths out of stored woolen sweaters) can help control mites in seed garlic, but should not be used for garlic that will be consumed.


Disease: Seedcorn maggot
Pathogen: Delia platura
Host Crops: Many vegetable crops including snap, kidney, and lima beans, onion, corn, turnip, pea, cabbage, and cucurbits. They cause the most damage in spring to newly emerging seedlings.

Photo Source:Lindsey du Toit, Washington State University Photo Source: Tim Waters, WSU Extension Educator for Benton and Franklin Counties

On-Line Resources:

Pacific Northwest Insect Management Handbook: Vegetable crop pests – Seedcorn maggot

Seed Corn Maggot. VegEdge, University of Minnesota

Seed Corn Maggot. UMass Amherst

See Diseases, pests, and other problems common to many vegetables: Seedcorn maggot


Common name: Two-spotted spider mite
Latin binomial: Tetranychus urticae (= T. bimaculatus = T. telarius).
Host crops: Numerous species of low-growing plants as well as a wide range of shrub and tree species. Normally not a significant pest of onion crops in the Pacific Northwest.

Photo Source: Carrie Wohleb, Washington State University Extension Educator Photo Source: Silvia Rondon, Oregon State University

On-Line Resources:

Pacific Northwest Insect Management Handbook. Chapter: Vegetables, Section: Common Pests of Vegetable Crops: Spider mite

Pacific Northwest Insect Management Handbook. Chapter: Supplement 1: Mite ID, Section: Common Mite Pests and Predators – pt. 1


Common name: Thrips, including western flower thrips, onion thrips, and other species.
Latin binomial: Various thrips including Frankliniella occidentalis (western flower thrips) andThrips tabaci (onion thrips). The latter is also a vector if Iris yellow spot virus (IYSV).
Host crops: Numerous plant species including many vegetables such as basilbroccoli,cabbagecauliflowercucumber, onion, potatopumpkinsquashtomato and watermelon.

Photo Source: Michael Bush, WSU Extension, Yakima, WA

On-Line Resources:

Pacific Northwest Insect Management Handbook. Chapter: Vegetables, Section: Onion pt. 2.

Onion Thrips, Washington State University Extension Fact Sheet, FS126E.

Vegetables: Onions, Garlic: Onion thrips, Washington State University Hortsense.

Western Flower Thrips Thysanoptera: Thripidae Frankiniella occidentalis,

Onion and Garlic Thrips, UC IPM Online, University of California

Life Cycle of Onion Thrips (Thrips tabaci)

See Diseases, pests, and other problems common to many vegetables: Western flower thrips.


Common name (of damaging stage): Wireworm (adults are called click beetles or snapping beetles)
Latin binomial: Ctenicera spp. and Limonius spp. Several kinds of wireworms are in the Pacific Northwest. Wireworms causing the most damage in irrigated areas are the Pacific Coast wireworm (Limonius canus), the sugar beet wireworm (L. californicus), the western field wireworm (L. infuscatus), and the Columbia Basin wireworm (L. subauratus). The Pacific Coast and sugar beet wireworms are the most common. Where annual rainfall is <15 inches, the Great Basin wireworm (Ctenicera pruinina) may be a problem, especially when irrigated crops are grown on sagebrush or dry wheat land. This species usually disappears after a few years of irrigation, but may be replaced by Limonius spp. which are favored by moist conditions. West of the Cascades, other wireworm species are pests, including Agriotes spp.
Host crops: All crops are susceptible to wireworm, but this pest is most destructive on beans,carrot, corn, grain, onion, potatoesspinach seed crops, and other annual crops in the PNW.

Photo Source: Tim Waters, WSU Extension Educator Photo Source: Gary Pelter, WSU Extension Educator Emeritus Photo Source: Tim Waters,
WSU Extension Educator
Photo Source:Lindsey du Toit, Washington State University
Photo Source: Lindsey du Toit, Washington State University Photo Source: Oregon State University – Oregon State Arthropod Collection.

On-Line Resources:

Pacific NorthwestInsect Management Handbook: Vegetable crop pests – Wireworm.

Managing Wireworms in Vegetable Crops. Ontario Ministry of Agriculture and Food

Wireworms. VegEdge, University of Minnesota.

Wireworms & Click Beetles. Washington State University.

Wireworm Field Guide – A guide to the identification and control of wireworms, Syngenta Crop Protection Canada, Inc.

Wireworm Biology and Nonchemical Management in Potatoes in the Pacific Northwest, N. Andrews, M. Ambrosino, G. Fisher, and S.I. Rondon, Pacific Northwest Extension Publication no. PNW607

See Diseases, pests, and other problems common to many vegetables: Wireworm.


Weeds

Common Name: Dodder
Latin binomial:Cuscuta spp.
Plants affected: Dodder is a parasitic plant that feeds on many other plant species. Dodder cannot photosynthesize, but produces haustoria that penetrate the host plant to absorb water and nutrients. Small, white to cream flowers are produced.

Photo Source: Lindsey du Toit, Washington State University

Online Resources:

http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7496.html

http://www.colostate.edu/Dept/CoopExt/4DMG/Weed/dodder.htm

http://pnwhandbooks.org/plantdisease/pathogen-articles/pathogens-common-many-plants/parasitic-plants-oregon

http://pnwhandbooks.org/weed/horticultural/vegetable-crops/onions


Common name: Yellow nutsedge
Latin binomial: Cyperus esculentus (Cyperaceae)
Plants affected: Any annual crop; the most seriously affected crops include onion and other plants with a light canopy and narrow range of herbicides available for use.

Photo source: Lindsey du Toit, Washington State University

On-Line Resources:

Yellow Nutsedge. Identification & Management of Emerging Vegetable Problems in the Pacific Northwest, Pacific Northwest Vegetable Extension Group.

Diseases, pests, and other problems common to many vegetables: Yellow Nutsedge.

Abiotic Problems

Disease: Basal plate splitting, basal plate blow-out
Causal agent: Uneven irrigation of onion fields increases the incidence of this disorder. If the soil is repeatedly over-irrigated, dried, and over-irrigated again, onion bulbs are likely to develop split basal plates. The wounding provides an opportunity for secondary microorganisms and bulb mites to colonize the bulbs.

Photo Source: Toni Grove, Whidbey Island Master Gardener Photo Source: Jenny Glass, Washington State University Plant Diagnostician

On-Line Resources: