Root and Crown Disease of Small Grains

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Utah Pest Fact Sheet

Published by USU Extension and UPPDL

Utah Plant Disease Control No. 41

 Revised March 1998


 

Root and Crown Diseases of Small Grains

Sherman V. Thomson/Extension Plant Pathologist
Scott C. Ockey/Plant Disease Diagnostician  

Wheat infected with Fusarium. Brown discoloration in the first internode as seen on the stem on the far left is a common characteristic of this disease. The arrow shows a pinkish area of fungal growth which is also commonly found on grains infected with Fusarium.
Wheat infected with the take-all fungus Gaeumannomyces graminis var. tritici. Image shows various infection severity states, (a) being the most severe and (c) being the least severe. The blackened crown area and absent roots are distinguishing characteristics of the disease.
Take-all symptoms on wheat and barley. (a) Wheat severely affected by the take-all fungus. (b) Wheat infected with take-all, not showing classic symptoms. (c) Barley infected with take-all slight browning of the first internode tissue.
Wheat infected with the snow mold fungus, Typhula spp. Arrows indicate the survival structures (sclerotia) commonly produced by fungi in this genus. Sclerotia are a diagnostic characteristic of this disease.

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.
  6. Effective chemicals include mancozeb (Dithane), difenoconazole (Dividend), captan (Captan), azoxystrobin (Dynasty), fludioxonil (Maxim), triadimenol (Baytan)

Take-All

CAUSE:  Gaeumannomyces graminis var. tritici

HOSTS:  Winter and 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.
  4. Effective chemicals include propiconazole (Tilt), benzimidizole (Topsin M).

 

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 Fusarium 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.

 

Precautionary Statement: All pesticides have benefits and risks, however following the label will maximize the benefits and reduce risks. Pay attention to the directions for use and follow precautionary statements. Pesticide labels are considered legal documents containing instructions and limitations. Inconsistent use of the product or disregarding the label is a violation of both federal and state laws. The pesticide applicator is legally responsible for proper use. This publication is issued in furtherance of Cooperative Extension work. Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Vice President for Extension and Agriculture, Utah State University.