The fungus that causes common root rot overwinters on crop residue and as soil-borne spores. The disease is widespread, because fungal spores survive for several years in the soil. It thrives in dry, warm soil conditions and compacted soil that restricts root growth. Over-application of nitrogen in dry conditions also favours the disease. Plants that are under nutritional stress, particularly phosphorus and potassium deficiency, are most vulnerable to infection.
Patchy plant emergence is often the first indicator of damage. The disease may not cause obvious aboveground symptoms, but scattered plants may ripen and die prematurely. Brown lesions usually appear on the crown area and on the roots. Occasionally, the aboveground parts of the plant display symptoms with the coleoptiles and lower leaf sheaves showing brown lesions. Diseased plants tend to be shorter and produce fewer stems and grains per head. Plants may also appear bleached and dead.
When infection is very severe, seedlings may die before or soon after emergence without showing significant visible damage. Less severe infections weaken plants and impact the viability of tillers, resulting in reduced yields.
- Apply adequate nitrogen, phosphorus and potassium to encourage vigorous root and shoot growth, allowing plants to better resist and tolerate infection.
- Early detection is necessary for diagnosis. Look for brown discolouration of the stem bases, roots, crowns and lower leaf sheaths.
- Rotation with other cereals and non-cereal crops will reduce disease levels.
- Avoid deep seeding, which increases disease severity.
- Minimum tillage may reduce disease incidence.