Pacific Northwest Vegetable Extension Group

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

Photo Gallery of Vegetable Problems

Lettuce

(Click on photo to enlarge)

General Lettuce Disease Management

Common Diseases of Lettuce, New South Wales Department of Primary Industries, Australia. Includes photos of disease symptoms on lettuce.


Diseases

Disease: Anthracnose
Pathogen: Microdochium panattonianum

Photo of Anthracnose on lettuce Photo of Anthracnose on lettuce Photo of Anthracnose on lettuce Photo of Anthracnose on lettuce

Photo Source: D.A. Inglis

Photo Source: D.A. Inglis

On-Line Resources:

Pacific Northwest Plant Disease Management Handbook: Lettuce (Lactuca sativa) – Anthracnose

Lettuce: Anthracnose, Washington State University Hortsense
 

Disease: Downy mildew
Pathogen: Bremia lactucae
Host crops: Lettuce and spinach.

Photo of severe symptoms of downy mildew on lettuce Photo of  downy mildew on lettuce Photo of sporulation of Bremia lactucae on the lower lettuce leaf surface. Photo of Sporangiophores and sporangia of Bremia lactucae.
Severe symptoms of lettuce downy mildew.   Sporulation of Bremia lactucae on the lower leaf surface. Sporangiophores and sporangia of Bremia lactucae.
Photo Source: Lindsey du Toit

On-Line Resources:

Pacific Northwest Plant Disease Management Handbook: Lettuce (Lactuca sativa) – Downy Mildew

See Lettuce: Downy Mildew. UC Pest Management Guidelines. UC IPM Online, University of California

See Models: Diseases: Lettuce: Downy Mildew. UC IPM Online, University of California
 

Disease: White Mold, lettuce drop, or Sclerotinia rot
Pathogens: Sclerotinia sclerotiorum
Host crops: Bean, various brassica vegetables, carrot, eggplant, lettuce, potato, tomato, etc.

Photo of symptoms resulting from basal infection of the stem from sclerotinia fungus residing in the soil Photo of  symptoms resulting from basal infection of the stem from sclerotinia of the fungus residing in the soil Photo of aerial infection of lettuce from ascospores released by the apothecia Photo of aerial infection of Sclerotinia sclerotiorum
Symptoms resulting from basal infection of the stem from Sclerotinia inoculum in the soil. Aerial infection of lettuce from ascospores released by the apothecia.
Photo Source: Lindsey du Toit Photo Source: Bo-Ming Wu
Photo of Sclerotinia sclerotiorum asci Photo of Sclerotinia sclerotiorum spore release Photo of Sclerotinia sclerotiorum
Sclerotinia sclerotiorum asci and ascospores. Sclerotinia sclerotiorum spore release from ascospores on the surface of infested soil. Sclerotinia sclerotiorum sclerotium with three apothecia.
Photo Source: Bo-Ming Wu

On-Line Resources:

Pacific Northwest Plant Disease Management Handbook: Lettuce (Lactuca sativa) – Drop {Sclerotinia Rot}

UC Pest Management Guidelines: Lettuce: Lettuce Drop. UC IPM Online. University of California.

Diseases of lettuce ( Lactuca sativa ) in Arizona: Leaf drop. Extension Plant Pathology, The University of Arizona.

Evaluation of Products to Manage Sclerotinia Leaf Drop of Lettuce in 2003. The University of Arizona Cooperative Extension.

Important New York Vegetable Diseases: LETTUCE: Drop (Sclerotinia sclerotiorum). Vegetable MD Online, Cornell University.

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

Insect/Mite Pests

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, potatoes, spinach seed crops, and other annual crops in the PNW.

Damage to Romaine lettuce caused by wireworms
Damage to Romaine lettuce caused by wireworms  
Photo Source: Photo courtesy of Rachel Bomberger, Washington State University

Online 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.

Our pages provide links to external sites for the convenience of users. WSU Extension does not manage these external sites, nor does Extension review, control, or take responsibility for the content of these sites. These external sites do not implicitly or explicitly represent official positions and policies of WSU Extension.

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