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MULTI-SITE INHIBITORS VITAL TO FUTURE-PROOFING CEREAL DISEASE CONTROL

With resistance to single site fungicides continuing to impede curative disease strategies and erode the protectant activity of existing chemistry, wheat and barley growers must use a diversity of active ingredients – including a multi-site – to ensure disease control programmes offer effective long-term protectant activity.

That is the latest advice from ADAMA UK, with the company’s Fungicides Technical Specialist, Andy Bailey, declaring that Arizona (500g/l folpet) will be crucial next spring, not only to provide adequate disease control in the coming season, but also to protect and prolong the efficacy of those actives which are threatened by resistance.

“The key advice when it comes to controlling diseases such as septoria in wheat and ramularia and rhynchosporium in barley is to keep ahead of the game by ensuring adequate protectant control is achieved,” Andy explains. “The timing of applications is therefore critical, as is the array of active ingredients used and the rate and frequency at which they are applied.”

In wheat, the continued reduction in the efficacy of triazoles against septoria is further complicated by the decreasing sensitivity of an increasing number of septoria strains to azoles and SDHIs: only BASF’s new isopropanol-azole fungicide, Revysol, offers effective curative action against septoria. However, as this is a single site active, it too is at potential risk of resistance and therefore needs to be protected to ensure its long-term efficacy. In barley, the position is slightly more favourable although the erosion in efficacy of azoles, along with SDHI sensitivity shifts and some resistance to strobilurin chemistry, means diseases such as ramularia and net blotch are becoming increasingly difficult to control.

“2021 will be the first full year cereal growers have had to protect their crops without the protectant benefit of chlorothalonil, so it is important to build a robust programme on a field-by-field and variety-by-variety basis,” Andy continues. “It is also important to ensure that fungicide programmes, as well as providing good protection against disease, also protect current and future fungicides against further erosion of efficacy.”

Mr Bailey therefore advises that the inclusion of folpet, which FRAG UK (Fungicide Resistance Action Group) describes as a ‘valuable tool to manage resistance and provides added levels of disease control whilst protecting and prolonging the efficacy of at-risk chemistries’, is a must.

“Disease control is about getting the right balance between efficacy, longevity of efficacy (resistance management) and return on investment,” Andy continues. “There will always be a trade-off, but by moderating the use of at-risk actives and including a multi-site in the programme, growers can achieve balanced and sustainable disease control.”

Arizona (500g/l folpet) is powered by ADAMA’s MSI (Multi-Site Inhibitor) Protech technology: as a multi-site inhibitor it works against various bio-chemical pathways within fungal cells (interfering with spore germination, cell division and mitochondrial energy production) which makes it less susceptible to resistance compared to single site actives.

Arizona is also the only multi-site fungicide that has been proven to protect and prolong the effective life of single site chemistries: modelling work carried out by Rothamsted Research has shown that, when applied in mixture, Arizona can double the life expectancy of epoxiconazole, while an ADAS modelling project has predicted that partnering Arizona with fluxapyroxad can significantly extend the latter’s in-field efficacy and life expectancy.

“Arizona provides valuable protection against septoria, rhynchosporium and ramularia, plus additional activity against rusts,” Andy continues. “In wheat, T1 remains the priority timing for including Arizona in terms of septoria control, yield response and return on investment, but Arizona is also flexible enough to be used at T0 and T2, thereby enabling it to be used as a resistance management tool throughout the season. Application at T0 and T2 is also advised in higher risk situations such as on disease susceptible varieties during periods of high disease pressure.

“Likewise, Arizona is the ideal protectant for barley crops where the key timing for the control of ramularia is at T2. It is also flexible enough to be used at T1 (the key timing for rhynchosporium) or at T0 should the season dictate a need for early season protection. To achieve effective control of both diseases a two-spray programme should be considered.”

Mr Bailey concludes that the best results will be achieved when Arizona is used as part of an integrated approach to disease management: “Selecting cereal varieties with robust disease resistance is going to become increasingly important as the erosion of curative fungicides continues,” he explains. “However, irrespective of varietal resistance ratings, the key is to prevent crops from being exposed to disease by ensuring adequate protectant activity is applied accurately and at the appropriate timing(s) before infection can take hold.”