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Flax Disease Update – August 2020

As most flax fields should be finished flowering, it is important to now focus on keeping the crop healthy and reaching harvest. Insect pests are no longer a threat to yield, but diseases are still a concern through to maturity.

Pasmo

When to look for:

  • Seedling stage to maturity
  • Favored when conditions are hot and humid

Symptoms:

  • Can cause defoliation and premature ripening
  • Circular brown lesions on leaves
  • Brown to black bands that alternate with green, healthy bands on the stem

Factors favoring development:

  • High humidity and moisture
  • Lodging favors development due to higher humidity
  • Spores are dispersed by rain and wind

Control:

  • Seed early
  • Use clean, disease free seed
  • Use lodging-resistant varieties
  • Good weed control to reduce humidity in the stand
  • Maintain a crop rotation of at least 3 years
  • Foliar fungicide applications around early flowering protect the crop, and reduce disease spread but may delay maturity
  • Invades the roots at any growth stage, from seedling to boll formation

Fusarium Wilt

When to look for:

  • Invades the roots at any growth stage, from seedling to boll formation

Symptoms:

  • Look for browning, dead plants exhibiting downward turn like a “shepherd’s crook”
  • Roots turn ashy grey

Control:

  • Use a resistant/moderately resistant variety
  • Maintain a crop rotation of at least 3 years
  • Use a seed treatment
  • Seedling to flowering stage

Seedling Blight and Root rot

When to look for:

  • Seedling to flowering stage

Symptoms:

  • Blighted seedlings turn yellow, wilt and die
  • Single plants, patches or gaps in the row
  • Roots have red or brown lesions, dark, shriveled
  • Flowering plants may wilt on hot days and turn brown prematurely

Control:

  • Use certified seed
  • Reduce seed cracking at harvest by adjusting combine settings appropriately
  • Use a seed treatment
  • Maintain a crop rotation of at least 3 years
  • Avoid planting legumes
  • Make sound agronomic choices at seeding

For more information on growing flax, download MFGA’s Quick Tips booklet. More in-depth details on Diseases Affecting Flax can be found here.

Article written by Morgan Cott, Agronomy Extension Specialist (Special Crops) with Manitoba Crop Alliance