Diseases of Oilseed Crops - Flax

Pasmo
Septoria linicola

What to look for?
(Sexual stage Mycosphaerella linicola)
Brown spots on leaves and stems and all above ground parts of the flax plant. Brown spots develop on leaves which may fall off. Brown spots on the stem may encircle the stem to form brown and green bands.This disease is prairie-wide and early infection reduces yield and quality .

Photo: Hoes

Picture description
Brown and green bands on the infected stem.

Management strategy
The disease is residue- and seed-borne, therefore, it is important to follow a crop rotation with clean, fungicide treated seed.

Rust
Melampsora lini

What to look for?
All five rust growth stages occur in the flax crop. Urediospores spread the rust from plant to plant and field to field.

Photo: Hoes	Picture description Uredia on flax boll is the most obvious stage of the pest.	Photo: Hoes	Picture description Stems and leaves infected in the growing crop.
Photo: Hoes	Picture description Pustules on the upper surface of leaves are the aecial stage.	Photo: Hoes	Picture description Spore producing aceia on flax leaf.

Management strategy
This disease is controlled primarily with resistant cultivars. If outbreaks occur then switch to a resistant cultivar. Bury infected crop residue and follow a crop rotation when disease outbreaks occur.

Fusarium Wilt
Fusarium oxysporum f. sp. lini

What to look for?
This disease is soil-borne where the fungus can persist for many years. Several races of Fusarium attack flax cultivars which are for the most part fairly resistant to this disease.

Photo: Hoes

Picture description
Yellow wilted leaves on infected flax plants.
Wilted flax shoots.

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Management strategy
Crop rotation is important in disease control. A measure of the soil-borne nature of this disease is that flax yields on land that has never grown flax previously may be much higher than flax crops grown on land once every three or four years. Flax cultivars may be resistant but not immune to this Fusarium wilt disease.

Aster Yellows
Phytoplasma

What to look for?
Bright yellow upper leaves on infected plants. This is the same insect vector and same phytoplasma disease that causes aster yellow in canola. This disease is transmitted by the six spotted leafhopper (Macrosteles fascifrons)

Photo: Hoes	Picture description Leaf-like greenish flowers that stand out in the crop.	Photo: Hoes	Picture description Bright yellow shoots.
Photo: Evans	Picture description Leaf-like flower parts.	Photo: Evans	Picture description Leaf-like flower parts while very conspicuous usually only occur at very low levels on perhaps 1 - 5% of the crop.

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Management strategy
None are economic.

Other Diseases of Flax

Seedling blight and seed rot caused by Rhizoctionia solani, Fusarium and Pythium spp.-- use recommended fungicidal seed treatments.

Stembreak and browning caused by Polyspora lini. This is a seed-borne disease that also survives in crop residues. In the flax crop, patches of heavily diseased plants appear brown--hence the name. Crop rotation and fungicidal seed treatment are control methods.

Powdery mildew caused by Oidum lini has shown up on the eastern prairies but yield losses are considered minor.

Sclerotinia stem rot (Sclertinia scleotorm)may occur in heavily lodged flax growing on land that previously grew sun flowers or canola crops that were susceptible to this fungal disease.

Seeds

Photo: Hoes	Normal healthy flax seed.	Photo: Hoes	Frozen damaged flax seed.
Photo: Hoes	Weather damaged flax seed.	Photo: Hoes	Blighted and moldy flax seed.

Photographs and information assembled and prepared for ARD by Dr. Ieaun R. Evans Agri-Trend Agrology Ltd.

Diseases of Oilseed Crops - Flax

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