Alfalfa
Lettuce

Impact
Common root rot is caused by a complex of soilborne fungi including
Helminthosporium and Fusarium species. Disease incidence occurs throughout the San Luis Valley on individual fields.
Losses of stand or yield are low, ranging up to 10 percent. Disease development depends on plant stress. If soil moisture is adequate, some symptoms may be present, but the plant is more able to compensate.
Light infections of common root rot occur throughout the San Luis Valley. Serious problems are rare.

Potatoes
Small Grains
Healthy grain production
Pests
Diseases
GPA Pan Trap Counts
Healthy Plants with intact subcrown node (left) ; and common root rot infected plants (right). (J Watkins, University of Nebraska)

Description and Symptoms

Infected plants appear stunted, have smaller root systems, and exhibit decay in the crown area.

Commonly, tillering is reduced regardless of degree of infection.

Part or all of the sub-crown internode, lower nodes, crown, and roots of an infected plant usually turn brown or reddish brown.

Brown coloring sometimes extends up the stem for a few internodes.

Small oval brown lesions may occur on the roots and sub-crown area.

Inoculum persists on cereal and grass hosts, in crop debris and in the soil. Some fungi can exist for months in the soil without a host.

Integrated Management

Rotate out of wheat or barley for one year to reduce fungal inoculum levels in the soil. Oats or broad leaf crops are suitable rotation crops.

Plant resistant cultivars when available.

Avoid soil compaction and provide good soil tilth to limit seedling stress.

Plant early at a proper seeding depth to permit uniform germination and emergence under cooler soil temperatures, which delay common root rot infections.

Maintain adequate nitrogen and phosphorus levels to encourage vigorous root and shoot growth, enabling plants to resist or tolerate infection.

Avoid plant moisture stress through accurate irrigation management.



This material is based on work supported by the San Luis Valley Water Quality Demonstration Project Best Management Practices Advisory Committee, Colorado State University Cooperative Extension, Farm Service Agency, Natural Resources Conservation Service, and the U.S. Department of Agriculture under authorization as 1991 U.S. Department of Agriculture Water Quality Demonstration Project.

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