Pacific Northwest Vegetable Extension Group

of Washington State University, Oregon State University, and University of Idaho

Photo Gallery of Vegetable Problems

Sweet Corn

(Click on photo to enlarge)

Diseases

Disease: Bacterial stalk rot
Pathogen: Erwinia species

Photo of Bacterial stalk rot on sweet corn
Photo Source: G.Q. Pelter

On-Line Resources:

Pacific Northwest Plant Disease Management Handbook: Corn (Zea mays) – Bacterial Stalk Rot

Corn: Root, stalk, and ear rots, Washington State University Hortsense

Common name: Common rust
Pathogen: Puccinia sorghi

Common Rust of Corn, (Video Presentation), Plant Management Network International

Differentiating Common Rust and Southern Rust of Corn, (Video Presentation), Plant Management Network International
 

Common name: Common smut
Latin binomial: Ustilago maydis (= Ustilago zeae)

Photo of common smut of corn Photo of common smut of corn Photo of common smut of corn Common smut on an ear of corn caused by Ustilago maydis.
Photos of common smut of corn. Common smut on an ear of corn caused by Ustilago maydis.
Photo Source: Karen Ward, Washington State University Plant Diagnostician Photo Source: Lindsey du Toit, Washington State University Photo Source:Silvia Rondon, Oregon State University


On-Line Resources
:

Corn Smuts. Oregon State University, University of Idaho, Washington State University.

Common smut of corn (Syn. boil smut, blister smut). APSnet.

Pacific Northwest Plant Disease Management Handbook: Corn (Zea mays) – Common Smut

Common Smut (Boil Smut), UC IPM Online, University of California
 

Common name: Head smut
Latin binomial: Sphacelotheca reiliana (Sorosporium reilianum = Ustilago reiliana)

Photo of symptoms of head smut on corn Photo of symptoms of head smut of corn tassel
Head smut gall on the ear of a corn plant. Head smut gall on the tassel of a corn plant.
Photo Source: Jerald Pataky, Professor Emeritus, University of Illinois at Urbana-Champaign

On-Line Resources:

Corn Smuts. Oregon State University, University of Idaho, Washington State University.

Pacific Northwest Plant Disease Management Handbook: Corn (Zea mays) – Head Smut
 


 

Common name: High plains disease
Latin binomial: High plains virus (HPV)

Photo of sweet corn leaf showing mottling from HPV Photo of sweet corn showing mottling from HPV Photo of Photo of sweet corn showing mottling from HPV in foreground and normal plant in background Photo of sweet corn in field showing gradation in incidence and serverity of damage from HPV
Close-up view of a sweet corn leaf showing mottling from HPV. Severe symptoms of high plains disease on sweet corn. Sweet corn plants without (top plant) and with (lower plant) symptoms of high plains disease. Gradation in incidence and severity of damage from HPV in a sweet corn field adjacent to a wheat field. The virus is vectored by the wheat curl mite, a pest on wheat that readily moves from wheat onto sweet corn when the wheat is drying down or is harvested.
Photo Source: Carrie H. Wohleb Photo Source: Gary Q. Pelter Photo Source: Lindsey du Toit

On-Line Resources:

High Plains Disease Caused by the High Plains Virus. Pacific Northwest Vegetable Extension Group August 2003 Newsletter.

Pacific Northwest Plant Disease Management Handbook: High Plains Disease
 

Common name: Southern rust
Pathogen: Puccinia polysora

Southern Rust of Corn, (Video Presentation), Plant Management Network International

Differentiating Common Rust and Southern Rust of Corn, (Video Presentation), Plant Management Network International
 

Insect/Mite Pests

Common name: Bird cherry-oat aphid
Latin binomial: Rhopalosiphum padi (L.)

Photo of aphids on sweet corn Photo of aphids on sweet corn
Live aphids, mummified/parasitized aphids, and shed aphid skins.
Photo Source: Photographer – Johnny Stark
Submitted by Jenny Glass

On-Line Resources:

Pacific Northwest Insect Management Handbook. Chapter: Vegetables, Section: Corn, Sweet (aphids to armyworm).


Common name: Corn earworm
Latin binomial: Helicoverpa zea

Corn earworm larvae feeding in an ear of sweet corn corn. Corn earworm larvae feeding in an ear of sweet corn corn.
Corn earworm larvae feeding in an ear of sweet corn.
Photo Source: Oregon State University HAREC-IAEP (Silvia Rondon’s lab)

Online Resources:

Corn earworm. Pacific Northwest Insect Management Handbook

Corn earworm. Integrated Peat Management, University of Illinois Extension.

Corn earworm. UC Pest Management Guidelines, Statewide Integrated Pest Management Program, University of California.

Corn Earworm Pest of Sweet Corn FS221E, Pacific Northwest Vegetable Extension Group


Common name:
Western corn rootworm
Latin binomial: Diabrotica virgifera virgifera

Western corn rootworm adult female. Western corn rootworm adult male.
Western corn rootworm adult female. Western corn rootworm adult male.
Photo Source: Oregon State University HAREC-IAEP (Silvia Rondon’s lab)

Online Resources:

Corn rootworm (larvae). Pacific Northwest Insect Management Handbook.

Plant Management Network "Focus on Corn" Webinars:

Adult Corn Rootworm Suppression - Lance J. Meinke, University of Nebraska-Lincoln

Decision Tree for Grower Management Options: Re-Learning Corn Rootworm Management in the Transgenic Era - Ken Ostlie, University of Minnesota

Larval Corn Rootworm Management - Robert Wright, University of Nebraska-Lincoln

Resistance Evolution and IRM for Rootworm - Aaron Gassmann, Iowa State University

Rootworm Biology and Behavior - Joseph L. Spencer, University of Illinois at Urbana-Champaign

Western corn rootworm in eastern Oregon, Idaho, and eastern Washington. In the Pacific Northwest, western corn rootworm has been found in corn crops in eastern Oregon, Idaho, and eastern Washington. Though it is not as abundant in the PNW as it is in the Midwest, WCR still has the potential to damage corn in the region.


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.

Photo of wireworm damage to onion bulb Photo of wireworms in soil around onion roots Photo of wirwirm in soil near onion roots Photo of field of onions showing wireworm damamge closeup of wireworm
         
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
Wireworms feeding on an onion plant in a bunching onion (CFC = cepa fisutlosum cross) seed crop. Photo of carrot showing wireworm and symptoms of wireworm damage Title Title
Wireworms feeding on an onion plant in a bunching onion (CFC = cepa fistulosum cross) seed crop. Damage to a carrot root from wireworms. A wireworm (click beetle larva). A wireworm feeding on plant roots.
Photo Source: Lindsey du Toit, Washington State University Photo Source: Doug Young, Professor Emeritus of Washington State University Photo Source: Oregon State University-Irrigated Agricultural Entomology Program (Silvia Rondon’s lab). Photo Source: Oregon State University-Irrigated Agricultural Entomology Program (Silvia Rondon’s lab).
A click beetle of the species Agriotes obscurus, the larvae of which are wireworms. A click beetle of the species Limonius californicus, the larvae of which are wireworms. A click beetle of the species Limonius canus, the larvae of which are wireworms.
A click beetle of the species Agriotes obscurus, the larvae of which are wireworms. A click beetle of the species Limonius californicus, the larvae of which are wireworms. A click beetle of the species Limonius canus, the larvae of which are wireworms.
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

Abiotic Problems Common to Sweet Corn

Common name: Air pollution or ozone injury
Cause: During very hot conditions in summer, combined with the presence of excessive air particulate matter, e.g., from wildfires, symptoms of air pollution and/or ozone injury have been observed in center-pivot irrigated sweet corn crops east of the Cascade Mountains in the Pacific Northwest USA.
Host Crops: Various vegetables such as bean, potato, and sweet corn.

Possible symptoms of ozone or air pollution injury to a sweet corn crop.
Possible symptoms of ozone or air pollution injury to a sweet corn crop.
Photo Source: Carrie H. Wohleb, Washington State University Extension


Common name: Injury to corn plants from the herbicide Prowl

Cause: The herbicide Prowl (active ingredient pendimethalin) is in the dinitroaniline (DNA) group of herbicides. Herbicides in this group inhibit root formation in susceptible plants. The herbicide blocks mitosis (cell division) in the root tip, causing short, club-like roots in corn. Plants that emerge may be stunted, and may have a red or purple margin to the leaves. Severely affected plants may die of drought stress, even if there is available water in the soil, as the plants cannot develop enough root system to support the water needs of the developing leaves/shoots. Roots that grow beyond the treated zone of the soil will start to grow normally again. DNA herbicides like pendimethalin can injure emerging corn plants if soil conditions are cool and wet after planting, or when corn seed is planted too shallow and/or comes into direct contact with the herbicide.

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Sweet corn root damage caused by the herbicide Prowl (pendimethalin).  
Photo Source: Tim Waters, Washington State University

Online Resources:

Herbicide Injury: Dinitroaniline Herbicides (Treflan, Rival, Bonanza, Prowl) injury to Corn, Excerpt from Agronomy Guide for Field Crops, Greg Stewart - Corn Industry Program Lead/Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA); Mike Cowbrough - Weed Management Field Crops Program Lead/OMAFRA.

Diagnosing Herbicide Injury in Corn, SS-AGR-365, Agronomy Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida (scroll to Section 5 on ‘Seedling Growth Inhibitors’ and the subheading ‘Dinitroanilines’).

Herbicide Mode of Action and Injury Symptoms, North Central Regional Extension Publication No. 377, University of Minnesota Extension Service (scroll to Section IV. ‘Seedling Growth Inhibitors’).

Cool, Wet Soils Can result in More Corn Injury from Preemergence Residual Herbicides, Integrated Pest Management, Division of Plant Sciences, University of Missouri.


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WSU Mount Vernon NWREC, 16650 State Route 536, Mount Vernon, WA 98273-4768, 360-848-6120
Contact Us: Lindsey du Toit and Carol Miles