Cereals: Tan Spot

Excerpt from Agronomy Guide for Field Crops (Chapter 6)

Order OMAFRA Publication 811: Agronomy Guide for Field Crop

Table of Contents

1. Incidence
2. Appearance
3. Disease Cycle
4. Management Strategies
5. Updates on Cereals: Tan Spot
6. Related links...

Incidence

Tan spot has been increasing in the province as a result of reduced tillage. Economic losses from tan spot have not been significant. However, the disease is often confused with Septoria leaf spot and misdiagnosis could result in unnecessary applications of foliar fungicides. Barley and oats are much more tolerant to tan spot than wheat.

Appearance

Tan spot begins on the lower leaves as small, tan-brown flecks that enlarge into oval- or lens-shaped tan lesions (5-15 mm) with a small, dark brown centre. A bright yellow zone or halo surrounds the tan lesion. The lesion is best viewed when the leaf is held to the sun.

Disease Cycle

The fungus survives on wheat residues. Disease development is favoured when prolonged, cool, cloudy, humid weather occurs early in the growing season. Spores are spread by the wind.

Management Strategies

Most wheat varieties are susceptible to tan spot. Include non-host crops such as other cereals, corn, soybeans and alfalfa in the rotation.

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Updates on Cereals: Tan Spot

• Field Crop Protection Guide - Publication 812
  • Cereals: Wheat: Tan Spot

Related links...

• Diseases
• Cereals

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