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Take-all Root Rot


© Kansas State University, Department of Plant Pathology

Pathogen(s) causing disease:

Gaeumannomyces graminisvar. tritici

Symptoms:

Detectable around jointing time, affected plants are stunted and yellow compared to healthy plants. This early phase of take-all usually goes unnoticed. If take-all is suspected early in the season, plants can be diagnosed in the Plant Diagnostic Laboratory by the presence of take-all fungal mycelium on the roots and crowns.

After heading time, take-all symptoms are much easier to detect. Whole plants begin to die and turn color prematurely. The white heads contain little or no grain. Plants may die individually or in large patches. Patches usually occur in wetter areas of the field. Occasionally whole fields are killed and this is how take-all gets its name. Since take-all is a root rot, affected plants pull out of the ground very easily. Diagnosis can be confirmed by the dark black discoloration on the roots and at the base of the stems.

Conditions:

 The take-all fungus survives between wheat crops in undecayed crop residue, on grassy weeds, and on volunteer wheat. Since the take-all fungus is short-lived, take-all is primarily a problem in continuous wheat. Take-all builds up slowly, so it's usually the third or fourth year of continuous wheat which is severely damaged.

In the fall, the fungus moves from the old residue onto the roots of young wheat seedlings. This requires good moisture and close contact between the old residue andthe new roots. Take-all infestations often originate from weedy grasses in ditches or waterways. Pieces of infected roots and crowns are simply dragged into the field during tillage. Smooth brome, cheat, wheatgrass, and wild barleys are all possible sources. The take-all fungus also produces airborne spores which may play arole in initiating new infections. Take-all is not carried in the seed or by insects.

Management:

Crop rotation is the most important method to control take-all. To avoid take-all or if take-all is present in a field:
  • Do not plant wheat more than two years in a row.
    • Barley, rye, and triticale are less affected by take-all than wheat, but they allow the fungus to survive on their roots. Therefore, rotation with these small grains will not reduce take-all if wheat is planted the next year.
    • Oats is an effective small grain rotational crop because it is not affected by take-all.
    • A one year rotation with canola between wheat crops controls take-all.
    • Plant non-host crops such as peanuts or cotton for at least one year between wheat crops.
    • In double-cropping systems, soybeans and grain pearl millet maintain take-all at a high level. Sorghum reduces take-all in a following wheat crop.
  • Avoid early planting. Planting earlier than the recommended period lengthens the period for infection in the fall.
  • Maintain soil pH at 6.0. pH values above 6.0 due to excessive liming favor take-all. Use soil tests to determine soil conditions.
  • Follow fertility recommendations to promote vigorous root growth. Excessive nitrogen and the nitrate form of nitrogen favor take-all. Ammonium forms of nitrogen do not favor take-all.
  • Maintain the proper levels of minor elements in the fertility program.
  • Avoid excessive tillage to reduce movement of infected plant debris which creates new infection sites. Unlike areas farther north, straw deterioration proceeds rapidly in minimum tillage in the Southest resulting in less fungal tissue to initiate infection.
  • Maintain adequate drainage in fields to promote root development.

Sources:

Kansas State University
University of Georgia

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