Tan spot

• Tan spot overwinters on standing wheat stubble, straw on the soil surface or partly buried by tillage and on bales of wheat straw.
• Spores, which are produced in the spring, are carried by the wind to growing plants. At least six hours of wetness are required for infection, and temperatures ranging from 15-28ºC (60-82ºF) with periods of dew favour infection.
• Spores produced on diseased leaves tend to spread during the growing season under periods of wet weather. Tan spot has increased on the prairies with the increase in reduced tillage, chem. Fallow and direct seeding, especially in tight crop rotations.

Scouting:

• Tan spot develops on both upper and lower leaves. The lesions first appear as tan-brown flecks that expand into lens-shaped lesions, similar to the lesions produced by the septoria leaf blotch fungus.
• Look for tan or brown flecks or yellow-rimmed blotches on the lower leaves.
• Look for withered and dead leaves later in the season. Examine the heads for infected seed.
• Seeds infected with tan spot will usually appear smaller and shriveled and may have a pinkish colouration, particularly in durum wheat.

Control:

• Include non-host crops in rotation.
• Bury infected crop residue (stubble).
• Apply a foliar fungicide.