Ramularia in barley: symptoms, lifecycle and risk

04 January 2022

Although Ramularia is an increasingly important disease for barley across the UK, it’s been established as an economically damaging one in Northern England and Scotland since 1998; this indicates the level of threat associated with the disease, which can cause yield losses of up to 1.0 t/ha in susceptible varieties.

With the right weather conditions - that is, wet spells followed by dry, sunny ones - it is able to spread further south. This is now being reported with increasing frequency. This only increases the threat, both to individual growers and the wider UK economy.

By understanding this devastating disease, barley growers are better able to look out for warning signs and identify Ramularia in their crop if the disease takes hold.

Ramularia symptoms in barley

Part of what makes Ramularia a challenging disease is that it can be difficult to identify; although it may be present from seed, symptoms often don’t emerge on previously healthy leaves until after flowering, showing on upper leaves first. The exception to this is when the crop is stressed, in which case visible signs may emerge earlier.

Typical symptoms of Ramularia can be summarised by the “5 Rs”.

  1. Reddish brown lesions
  2. Rectangular shape
  3. Restricted by leaf veins
  4. Ringed with a yellow margin of chlorosis
  5. Right through the leaf

If infection levels are high, leaves may deteriorate rapidly. On dead leaves, the lesions often show as black spots with visible fungal spores.

Ramularia lifecycle

The Ramularia fungus often starts life in the seed, moving systematically with new plant growth. However, the fungus can also be airborne, with spores produced on crop debris infecting plants.

As mentioned previously, visible symptoms aren’t present right away; whilst earlier in the season infection may appear in senescing leaves, generally signs of infection emerge on the top leaves after flowering. As the season moves on, growers may begin to see rows of white spores on the underside of infected crops with a hand lens, which then become easier to see with the naked eye as the leaves deteriorate.

Stressed crops are more likely to exhibit visible symptoms, particularly if exposed to high rainfall and light levels after flowering.

Risk factors

Like with many crop diseases, the first, and probably most important risk factor is the weather. It is thought that long periods of leaf surface wetness at stem extension could influence severity of Ramularia, as well as cool nights and heavy morning dews. In addition, under cool conditions, the crop may be slow to grow away from infection; this is a further factor allowing Ramularia to colonise the crop faster and more extensively.

There are also other factors to be considered in Ramularia risk, including the variety grown. Some barley varieties are more susceptible to disease than others, so by selecting a resistant crop on the recommended list, risk may be reduced. However, it is important to point out that just because a variety demonstrates some level of resistance, it may not be completely immune – particularly in tough disease years. Previous cropping, cultivation system and high light levels after flowering are additional risk factors.

Control

The most effective method of control currently available is through the use of fungicides; this usually involves a preventative spray between growth stage 45-49, followed by later applications until growth stage 59. Unfortunately, once symptoms emerge on the upper leaves post-flowering, the effectiveness of treatment is minimal.

However, another new tool for growers is SwiftDetect. This unique, rapid disease detection test is able to identify down to just a few pathogen cells of Ramularia infection, even in early growth stages. The test can prove a useful tool in the control of crop disease, by:

  • Giving growers an early warning: actionable insight into the level of disease, even before visible signs emerge
  • Quantifying disease levels: enabling tailor-made fungicide regimes, based on the actual level of disease in your crop
  • Measuring levels over time: understanding Ramularia infection spread patterns in your crop, facilitating better predictions in the future
  • Allowing you to react in real-time: rapid turnaround, with results reflecting current disease levels emailed to you within 1 business day upon receipt of your sample
  • Spray timings: SwiftDetect gives you the insight to spray according to disease level, instead of blanket spraying according to growth stage, resulting in more effective treatment

Register your interest in SwiftDetect! SwiftDetect is currently closed for the season but will be back in March 2022 able to detect Ramularia in Barley, plus Septoria, Yellow Rust, Brown Rust and Mildew in wheat. Click here now to register your interest and be among the first to hear when SwiftDetect is available.