Take-all

Take-all often appears as patches of stunted, uneven, yellowing plants that ripen early. Pulling affected plants reveals blackened, brittle roots and a shiny black discoloration of the stem base beneath the leaf sheaths. The most striking above-ground symptom is the presence of whiteheads: heads that turn white and remain empty or produce shrivelled grain because the root system has failed.

Gaeumannomyces tritici survives between crops as dark strands of fungal growth (hyphae) on infected cereal roots and residue in the soil. When a new cereal crop is grown, the fungus grows from this residue onto the roots, spreading along and between roots as they contact infected debris. Because it depends on cereal roots, its populations rise under continuous cereals and fall when a break crop removes the host.

• Infected cereal residue and root debris carry the fungus between crops
• The fungus grows from residue onto the roots of the next cereal crop
• Successive cereal crops allow inoculum to build up in the soil
• A non-host break crop starves the fungus and lowers its populations

Wheat is the most susceptible host, with barley, triticale, rye, and many grasses also affected; oats are comparatively resistant to the wheat form and are sometimes used as a break. Moist soils, near-neutral to alkaline soil pH, and poor early root growth all tend to increase severity, as do continuous cereals and grass weeds that maintain the fungus.

• Continuous or closely rotated cereals that keep a host present
• Moist soil conditions that favour root infection
• Higher (neutral to alkaline) soil pH, which tends to increase disease
• Grass weeds and volunteer cereals that host the fungus between crops

Because take-all is soil-borne and cereal-dependent, rotation is the cornerstone of management, supported by practices that keep roots healthy and reduce the host bridge between crops. There is no in-crop rescue treatment once roots are heavily rotted, so prevention is essential.

• Use rotation with non-host break crops to reduce soil inoculum
• Control grass weeds and volunteer cereals that maintain the fungus
• Encourage vigorous early root growth through good establishment and balanced nutrition
• Manage residue and avoid practices that spread infected debris
• Track field history, since risk is often highest in the second and third successive cereals