Published on 01/07/2020
In the UK, resistance alarm bells sounded over a decade ago. In New Zealand, 2018 saw the ‘perfect storm’ with a wet barley growing season and resulting high disease pressure, feeding Ramularia’s aggressive ability to mutate. The result was crop losses of up to 30 per cent.
While multi-site protectant Phoenix Fungicide (Phoenix) now provides a very effective addition to the Ramularia control toolbox, the sudden failure of SDHI fungicides was a sobering reminder of the constant risk resistance poses to crop security. According to FAR’s Autumn Round Up 2020, Plant & Food Research had identified three SdhC mutations that impacted on the performance of SDHIs against Ramularia in barley. In 2019, microplate assays found that 100 per cent of the Ramularia isolates collected in the 2018-19 season were insensitive to this chemistry.
Crop protection company Adama NZ, a long-time advocate of adding multi-sites to control Ramularia in barley and Septoria in wheat, described the collapse as ‘dramatic’.
The failure of SDHIs against Ramularia saw growers re-assessing programmes, with Adama NZ’s multi-site Phoenix becoming a key part of disease control. Approved for Ramularia in time for the 2019 season, Phoenix was already proven in the UK and Europe, and in NZ against Septoria in wheat. There is currently no recorded resistance to Phoenix’s active, folpet, anywhere in the world, and Adama’s testing has confirmed no sensitivity shifts against Septoria. Adama NZ recommends using Phoenix with all-rounder fungicide Bolide or other triazole chemistry. NZ 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. This performance is further strengthened when Bolide is tank-mixed with Phoenix.
Ramularia’s early season invisibility and devastating consequences mean it is safest to presume it is already in the crop. If only one spray of Phoenix is being applied in barley, then T2 is the optimum timing. This ensures that leaves two and three 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. While recent drier seasons may have reduced some Septoria pressure in wheat, there is still a risk to yields, particularly with high-value, more susceptible varieties. Adama NZ says its advice, as for barley, is to ensure Phoenix is first in the tank. Application at T1, with a DMI such as Bolide, is strongly recommended and supported by industry bodies.
For more detail, contact your Adama NZ commercial manager