Winter wheat diseases in autumn, winter and spring

If you want to achieve high yields, it is important to take care of reliable crop protection in advance and, if necessary, respond quickly to emerging risks. The first stage in securing a good harvest is high-quality seed material. It is often impossible to detect wheat seed diseases visually. That is why the best solution is detailed seed testing, carried out by an agricultural laboratory using specialised methods and equipment.

The next stage is monitoring the condition of crops during the growing season. Below, we look at the main wheat diseases so that symptoms can be recognised in time and effective protection measures can be applied.

Crown and root rots

Some autumn and spring wheat diseases are particularly dangerous. Crown and root rots belong to this category. These diseases are caused by a complex of pathogens and are especially harmful to young, not yet fully developed plants. Rots affect the root system and the lower part of the stem. Most often, they have a mixed aetiology, meaning they are caused by several pathogens at the same time.

Weather conditions are an important indirect indicator for monitoring, as they are directly linked to the biological activity of pathogens. For example, moist and moderately cool weather promotes the development of soil-borne and root pathogens, including Fusarium spp., Pythium spp. and Rhizoctonia spp.. In contrast, increased humidity and warm conditions favour the development of Bipolaris spp., which affects stems and tillering nodes, causing crown rot.

Typical field signs indicating these wheat diseases at the seedling stage include:

• slowed plant growth;
• seedling lodging;
• thinned crop stands;
• weak development of the secondary root system.

Typical field signs indicating these diseases from the tillering stage to stem elongation include:

• browning or reddening of roots;
• necrosis on the subcrown internode;
• suppressed growth and weak tillering.

Typical field signs indicating these winter wheat diseases in mature plants include:

• yellowing of the lower leaves;
• low thousand-seed weight;
• premature ripening and “whitehead” symptoms.

Affected plants lose vigour and turn yellow. The crown or root collar becomes blackened, thinner and soft. Factors that intensify disease development include failure to observe crop rotation, waterlogging, sharp fluctuations in moisture levels and infected seed.

Snow mould

When considering fungal diseases in wheat, special attention should be given to snow mould, caused by Microdochium nivale (syn. Fusarium nivale). This disease is typical of the winter period in winter crops.

The main conditions for disease development are early and prolonged snow cover, temperatures from -5 to +5 °C and overly dense crop stands. In early spring, symptoms that remained hidden under the snow become visible: patches of yellowed or browned plants, lodging, and watery spots on the leaves, which later become covered with white-pink or grey fungal mycelium.

Affected plants rot, darken and die, creating characteristic gaps in the field. The disease causes particularly significant damage in years with thick and long-lasting snow cover.

Powdery mildew

Powdery mildew (Erysiphe graminis) is a common fungal disease of winter wheat. It infects plants in autumn and continues to develop actively in early spring, especially under mild winter conditions and cool, humid weather.

The first symptoms appear already at the seedling stage: a white, powdery coating forms on leaves, leaf sheaths and stems. Over time, it becomes denser and turns grey or brown. In later stages of disease development, black dots appear — the fruiting bodies of the fungus.

Autumn infection weakens plants, reduces their frost resistance and subsequently has a negative effect on photosynthetic activity.

Rust diseases

Winter wheat diseases in spring may appear as rust infections. They are characterised by the formation of deposits and pustules on affected plant tissues. The pustules are filled with brown or yellow-brown spores, which resemble rust in colour. Three main types are distinguished: yellow rust, stem rust and brown rust.

The pathogens are microfungi of the genus Puccinia spp.. Infection usually occurs in spring, although under favourable conditions it may also take place in autumn, with the pathogen surviving on crops during a mild winter.

Disease development is promoted by moderate temperatures ranging from +8 to +17 °C, high air humidity, including dew and fog, and overly dense crop stands.

Septoria leaf blotch

Septoria leaf blotch (Septoria tritici) is a common fungal disease of wheat during the autumn-spring period. It affects leaves, leaf sheaths and ears, significantly reducing crop productivity.

The disease is favoured by prolonged leaf wetness and temperatures from +10 °C. Septoria leaf blotch is characterised by irregular light-brown or grey spots. Black dots — pycnidia — appear in the centre of the lesions.

Infection reduces the assimilative leaf area, weakens plants in spring and lowers thousand-seed weight.

Other leaf spots

In addition to Septoria leaf blotch, other leaf spot diseases caused by a range of pathogens are also common in winter wheat during the autumn-spring period. They affect the leaves, reduce photosynthetic activity and weaken plants.

Tan spot (Pyrenophora tritici-repentis) appears as yellow or light-brown spots with a dark margin. A characteristic sign is a chlorotic zone around the lesion, which can be seen in publicly available images. Cool and humid weather favours disease development. The result is premature leaf death and reduced grain weight.

Alternaria leaf spots (Alternaria spp.) appear as small dark spots with concentric rings. The pathogen usually develops on weakened plants and damaged tissues. Sharp temperature fluctuations and increased humidity are required for its development.

Cladosporium leaf spot (Cladosporium spp.) is saprotrophic in its mode of nutrition. On its own, it does not pose a major threat, but in combination with other pathogens it reduces leaf viability. Olive-brown spots with a velvety coating form on the leaves.

These winter wheat diseases develop more actively in spring and autumn under conditions of frequent rainfall, high humidity and moderate temperatures.

Main protection measures against cereal diseases

An effective protection system for winter wheat in autumn and spring is based on a combination of preventive and technological measures aimed at minimising infection pressure and ensuring stable yield. The main measures include:

• Seed treatment with fungicidal products approved for use in Ukraine. This is a key stage that provides initial crop protection. The use of seed treatments with systemic and contact action helps block a broad spectrum of seed-borne and soil-borne pathogens.
• Compliance with scientifically justified crop rotation. Monoculture significantly increases the risk of infection build-up. Suitable preceding crops for wheat include peas, oilseed rape and black fallow. It is recommended to limit areas sown after cereal crops to 15-20%, which reduces the likelihood of disease development.
• Laboratory grain analysis, including seed material testing. Visual seed assessment does not allow hidden infections to be detected. Therefore, before sowing, diagnostics should be carried out in agricultural laboratories. This makes it possible to determine the infection level in time and select optimal seed treatment products.
• Agrotechnical measures. Winter wheat diseases in autumn and spring can be prevented by regulating crop density, observing optimal sowing dates and ensuring balanced plant nutrition.

When the first symptoms appear, action should not be delayed. Plants should be sent for phytopathological examination for accurate diagnostics and determination of the species composition of the pathogens. This allows the problem to be addressed precisely, rather than relying on assumptions or applying fungicides that do not belong to the relevant target group.