Ramularia Resistance in Barley
Ramularia Fungicide Toolbox
Like with Septoria in wheat, the Ramularia fungicide toolbox initially covered three groups of chemistry: SDHIs, DMIs and multi-site fungicides. However, with the sudden and dramatic loss of SDHI chemistry, the toolbox is now limited to DMIs and multi-sites only.
SDHIs
In 2016/2017 it was already reported that Ramularia was difficult to control, with sensitivity reduced further a year later. A “perfect storm” of a wet 2018 barley growing season and the resulting high disease pressure fed Ramularia’s aggressive ability to mutate. In 2019, microplate assays found that 100 percent of the Ramularia isolates collected in the 2018–19 season were insensitive to this chemistry. It only took three seasons to render SDHIs ineffective.
DMIs
With SDHI and strobilurin chemistry lost, DMIs (DeMethylation Inhibitors) such as BOLIDE® are key to control Ramularia. To ensure they keep providing effective control, they need to be protected by multi-sites.
Multi-sites
Multi-site fungicides such as PHOENIX® Fungicide (PHOENIX) are critical to control and manage Ramularia. PHOENIX (folpet) affects several different metabolic sites within the pathogen and is protectant in action. Folpet has no known resistance and remains at a very low risk of resistance developing in cereal pathogens.
Break the Resistance Cycle with PHOENIX and BOLIDE
Win the fight against key diseases by combining PHOENIX and BOLIDE, the ultimate duo for resistance management.
Ramularia can cause extensive damage to the upper leaves of spring and autumn barley once crops have finished flowering, resulting in reduced crop quality and yield.
Effective Control with Multi-Site Chemistry
Fortunately, multi-site chemistry like PHOENIX provides excellent protectant control of Ramularia when applied in a tank-mix with a DMI such as BOLIDE at the correct timing, before the outbreak in the crop.
Unlike other modes of action, multi-site fungicides are less susceptible to resistance development and, as such, remain effective even against resistant strains of Ramularia. Adding PHOENIX is therefore vital to providing effective protection.
The FAR Crop Action Edition 134, 14 September 2018 reported that adding PHOENIX to DMI Proline® in a two-spray programme gave significantly better control of Ramularia than mixes of DMI with SDHI and, also, the highest yield. That finding was reinforced in FAR’s virtual Autumn 2020 Round Up, which too reported good control from PHOENIX mixed with Proline.
Why is Application Timing Critical?
Symptoms of Ramularia infections appear late in the season. Left unchecked, infections can cause yield losses of 0.5-1 t/ha. Grain quality can also be affected as a result of poor grain filling resulting in ‘thin’ grains, which produce higher screenings.
To take full advantage of the yield potential of barley, spray programmes should therefore be designed to maximise the crop’s green area index by reducing the effect of disease on tiller numbers early in the season and to keep the entire plant as green as possible for as long as possible.
When to Apply? At T1 and T2!
ADAMA recommends using PHOENIX with all-rounder fungicide BOLIDE or other DMI chemistry. New Zealand trials with BOLIDE have not only shown outstanding control for a wide range of diseases comparable to industry standard SDHIs and DMIs, but also highly effective Ramularia control.
If only one spray of PHOENIX is being applied in barley, then T2 is the optimum timing. This ensures that leaves 2 and 3 are protected.
For best results though, a programmed approach suggests even higher levels of Ramularia control when using Phoenix at both T1 and at T2. These applications maximise the crop’s green leaf area index to maximise yields by promoting healthy spikelet and ear development.
PHOENIX is limited to two applications only. For more details on application please read the PHOENIX label.
Andy Bailey on Ramularia Resistance
