As soil and air temperatures increased in late March and April, winter barley crops burst into life. Crops quickly switched from their vegetative stage with the production of leaves and tillers to the reproductive stage as seen through the production of nodes and the extension of the stems. Unfortunately, not all crops appear to have done this equally.

In some fields, patches appeared to be stunted. Such patches can be the result of a range of conditions, from disease through to poor nutrition. While barley yellow dwarf virus (BYDV) is evident in many places, and responsible for some of these stunted crops, others don’t appear to have the typical BYDV symptoms.

Upon closer inspection of such patches, distinct problems are obvious with the roots, which will have a major impact on the health of the plant. This will become more evident as the crop’s requirement for nutrients increases to feed its increasing canopy size.

It is important to identify what is causing these problems so that action, both for the remainder of this season and for future seasons, can be taken. Unfortunately, the ideal growing conditions in late autumn that promoted good crop establishment also promoted fungal growth. Therefore, it is no surprise that in seasons where crops show excellent potential, some will lag behind and suffer. Below are some of the main diseases encountered so far this season.

Take-all

This is present to varying degrees every season and can cause serious yield reductions in wheat and barley crops. It is most severe following an autumn and winter that had mainly warm moist soils and when these are followed by a dry summer. As most winter barley crops will have completed grain filling before the drier periods of July and August, the disease is often thought of as more of a problem in wheat.

While symptoms generally manifest through premature plant senescence later in the season, stunted growth can be observed in late spring, especially where severe infections have occurred. The disease causes blackening of the roots, which are often brittle and can easily break away from the plant when it is pulled from the soil. The best diagnostic tool for this disease is the identification of black runner hyphae on the roots using a lens.

It is often most severe in the second, third and fourth years of a cereal crop, with a decrease in severity often occurring after that due to a build-up of a natural protection within the soil referred to as “take-all decline”. Such protection is not always guaranteed and severe infections can often occur in continuous cereal rotations.

Different strains of the fungus exist and the most common strain, which infects wheat and barley, does not affect oats. However, a rarer strain which affects oats can also infect wheat and barley. In fields where severe infections have occurred, the best control is achieved through rotations with non-cereals and ensuring both cereal volunteers and grass weeds are kept to a minimum.

Rhizoctonia stunt

More commonly known by tillage farmers as a disease of potatoes, specific rhizoctonia strains do affect cereal crops. While also causing a darkening of the roots, rhizoctonia infection is generally more of a brown colour than the blackening seen with take-all. Typical diagnostic features of the disease include darkening or restriction of roots at various different points. In severe cases this can make them look like a string of sausages. In addition, these restrictions can be complete and when plants are removed from the soil it can appear as if the root has been snipped or pinched off.

The disease is often more severe in winter barley than wheat. As the fungus grows in the soil, it can infect individual plants or large patches. Relying on fungal networks, the disease is more prevalent on lighter soils with minimum tillage where large networks of fungus can be established.

If infections have been observed, inversion tillage, which breaks the fungal networks, is recommended.

It is an opportunistic pathogen which is present in most soils at some level and strikes crops which are struggling for some other reason.

Omphalina patch

While it is much less common than either Take-all or Rhizoctonia, Omphalina patch has been reported in a number of cereal crops this season. Manifesting itself as fungal masses on the roots of cereals, it restricts the capacity of the plant to take up and transport nutrients.

Symptoms are mostly observed in early spring as severely stunted patches which, as with Rhizoctonia, can range from a single plant to larger patches.

In addition to fungal masses on the roots, which can look like galls, small fungal masses can also be observed in the soil. Without close inspection, the disease can be confused with cereal cyst nematode damage. Depending on the severity of infection, affected plants and patches can recover some of the vigour they may have lost in early spring growth.

Often the disease is accompanied by the appearance of mushroom-like growths on the soil in the infected patches between mid-January and early March.

As it can survive in the soil as resting bodies (sclerotia), and is capable of infecting numerous different species including grass, it is recommended that rotation with a non-cereal, non-grass crop follows.

Crop symptoms appear quite like hunger in that affected plants lose colour and leaves begin to die off and then the volume goes out of the infected patch initially. These patches become more visible when spring growth accelerates.

Relatively little is known about the disease or its control, but foliar fungicide treatments are not believed to have any major impact on disease suppression.