Plant Disease Control No. 41
Revised March 1998
Root and Crown Diseases of Small Grains
COMMON ROOT, CROWN , AND FOOT ROT
Cause:Helminthosporium sativum
Hosts: Winter and spring wheat, barley.
Diagnostic Symptoms: Subcrown internode is dark brown in color. Dark streaks may extend into the crown and a short distance into the culm. Diseased plants occur obvious foliar symptoms, but yields are reduced by 10- 25%.
Controls:
1. Rotate 2 or more years out of small grains.
2. Seed winter grains later, when the soil temperature at the 3" depth is 60 F or below.
3. Oats and other small grains are supportive hosts and should not precede wheat in rotations.
4. Disease severity can be reduced by moldboard plowing and by reducing the seeding rate and the amount of fall applied nitrogen.
5. Imazalil seed treatment may reduce losses.
TAKE-ALL
Cause: Gaeumannomyces graminis var. tritici
Hosts: Winter or spring wheat, barley.
Diagnostic Symptoms: The base of the stem under the lower sheath becomes covered with a coal-black fungal growth. The roots turn coal-black in color. Plants are stunted, mature early, and have white, empty heads.
Controls:
1. Maintain a good level of nitrogen, using an ammonia based fertilizer. Chloride fertilizers are reported to decrease damage.
2. Do not follow alfalfa that was heavily infested with cheatgrass (Bromus tectorum).
3. Avoid planting wheat following wheat unless long-term monoculture is planned.
EYESPOT OR STRAWBREAKER
Cause: Pseudocercosporella herpotrichoides
Hosts: Winter wheat and winter barley.
Diagnostic Symptoms: Elliptical or eyespot lesions develop on the lowest leaf sheaths and adjacent internodes just above the soil line. Diseased plants tend to mature early and produce white heads with incompletely filled heads. Lodging is common.
Controls:
1. Seed later in the fall when the soil temperature at the 3" depth is 60 F or below.
2. Rotate to other crops besides cereals for at least two years.
3. A Benlate foliar spray after tillering will reduce losses.
DRYLAND ROOT, CROWN, AND FUSARUIM FOOT ROT
Cause: Fusarium spp.
Hosts: Winter barley, oats, and wheat.
Diagnostic Symptoms: The roots turn a brown color and the subcrown internode becomes discolored. At the boot stage the roots and the subcrown internode are uniformly dark brown. The lower stem extending above the first node may be streaked of uniformly brown. A pink fungal growth may be seen between the sheath and the stem. After heading, white heads may develop that have shriveled or have no kernels. Lodging may occur in individual plants or in patches.
Controls:
1. Seed later, when the soil temperature at the 3" depth is 60 F or below.
2. Rotate 2 or more years out of small grains.
3. Disease severity can be reduced by moldboard plowing and by reducing the seeding rate and the amount of fall applied nitrogen.
SNOW MOLD
Cause: Typhula idahoensis, T. incarnata, and Fusarium nivale
Hosts: Winter wheat.
Diagnostic Symptoms: Found in areas with heavy, prolonged snow cover. A felty white or pink fungus may develop on the plants that is evident as the snow cover disappears. The plants have a mushy, water-soaked appearance after the snow melts. The leaves dry into a matted mass of dead material. Typhula spp. produce small, round, brown sclerotia, the size of pepper grains in the leaf tissue. Fusarium - produces pink mycelium on decayed foliage.
Controls:
1. Applications of fly ash or graphite onto the snow in January or February accelerates snow melting, which prevents the disease from developing.
2. Some varieties of wheat show tolerance but there are no resistant varieties.
Sherman V. Thomson/Extension Plant Pathologist
Scott C. Ockey/Plant Disease Diagnostician
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