Wet weather diseases like rhynchosporium and net blotch are the main threats to winter and spring barley in most seasons, however the risk from mildew and ramularia can also be significant depending on conditions and varieties grown, said Dr. Steven Kildea, senior research officer at Teagasc.

“Managing the disease threats in barley is all about building integrated cultural and chemical control strategies around the specific risk factors in individual situations,” he said.

Barley yields are driven by tiller number, so protecting crops during the primary development phase is critical to prevent tillers being lost to disease, compromising yield potential.

Although individual spray programmes depend on location, variety and seasonal weather, Steven says many winter barley crops, particularly those grown in milder, wetter parts of southern Ireland, often require a three-spray fungicide strategy to protect tillers and maximise grain fill by maintaining a healthy canopy as long as possible.

Timings for a three-spray programme typically see the first application at the end of tillering, a second at stem extension (growth stage 31) to protect leaves two and three, and a final spray around booting/awns emerging to reduce the risk of ramularia developing later in the season.

Spring barley

“In spring barley, the whole growing season is condensed into a much shorter period, but the focus should still be on maximising tillers and protecting the upper canopy,” Dr. Kildea added.

David Leahy, BASF’s business development manager in Ireland said many growers tend to prioritise the later fungicide applications in barley and often neglect the importance of the T1.

“This strategy can work, but if you don’t fully control disease at that first timing, there’s always a risk of losing tillers and compromising yield. In a post-chlorothalonil era, robust disease control at both timings is important as it helps mitigate the threat from ramularia later in the season,” he said.

“This is largely down to ramularia being a stress-induced disease.

“Barley can be just as rewarding as wheat if managed correctly. This is not purely due to disease control, but equally down to good basic agronomic principles. If the disease risk is there, growers should invest in the crop to push yield and gross margin.”

Traditionally, many growers have looked to prothioconazole as the most effective azole against net blotch, however robust rates are now needed to achieve reasonable efficacy, he said.

Although resistance to strobilurin fungicides caused by the F129L mutation is an issue within the European net blotch population, some products still offer good control, Dr. Kildea added.

Pyraclostrobin is the most effective, as it is not affected by the F129L mutation, so will even control resistant strains, he said.

Figure 1 Data from a glasshouse trial showing effective control from F500 (pyraclostrobin). Control from azoxystrobin is less than that from trifloxystrobin

Comet, Modem, Priaxor and Serpent are the main F500 options in Ireland. Using these in combinations with it’s pack partner, Decoy 250 (prothioconazole) provides enhanced protective and curative fungicide activity.

Minimising crop stress can help reduce the risk of ramularia developing, Dr. Kildea noted, adding:

“Growers can’t do a lot about the weather, but we can try to establish crops well in the first place and keep them clean and well-nourished to reduce the risk of stress later in the season.”

Figure 2 Decoy 250 + Comet 200 delivered unrivalled disease control and green leaf area retention in Ireland in 2021. Treatments made at T1 timing only

Barley fungicide tips:

  • Assess disease risk, based on variety scores, rotation and weather;
  • Tailor product choices to risk, adjusting plans according to the season;
  • Alternate chemistry and use different modes of action to reduce resistance;
  • Be prepared to invest in barley to maximise yield potential;
  • Consider a three-spray programme in higher disease pressure situations:
    • T1 Tillering (GS 25-30):
      Apply an early spray to prevent tiller loss.
      Decoy 250EC + Comet 200 is an excellent product at this timing, providing the most effective T1 combination for the control of rhynchosporium, net blotch and mildew, as well as proven physiological benefits of F500;
    • T2 Stem extension (GS 31-33):
      Use Azole / SDHI based chemistry to maintain intervals and protect the upper canopy;
    • T3 Flag leaf/ booting (GS 39-49):
      Apply a broad spectrum fungicide.
      Decoy + Priaxor is the most broad-spectrum fungicide for the final spray timing on winter and spring barley crops, with market leading rhynchosporium control and the power of Xemium for maintaining straw quality.

For more information on disease control products for barley, click here.

BASF