Lettuce

Diseases

Insect/Mite Pests

• Wireworm

General Lettuce Disease Management

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

Diseases

Anthracnose

Disease: Anthracnose
Pathogen: Microdochium panattonianum

On-Line Resources:

• Pacific Northwest Plant Disease Management Handbook: Lettuce (Lactuca sativa) – Anthracnose.
• Lettuce: Anthracnose, Washington State University Hortsense.

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Downy mildew

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

Online 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.

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White mold, lettuce drop, or Sclerotinia rot

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

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.

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Insect/Mite Pests

Wireworm

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.

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.
• Wireworm Field Guide (pdf) – 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.

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