Future-proofing sustainable disease control

With resistance to single-site fungicides continuing to impede curative disease strategies and erode the protectant activity of existing chemistry, ADAMA is encouraging wheat and barley growers to use a variety of active ingredients, including a multisite, to boost long-term protectant activity.

In a bid to prevent resistance and boost efficacy in at-risk single-site actives, ADAMAs multisite fungicide Arizona (500g per litre folpet) has been designed to protect against septoria in wheat and rhynchosporium with additional protection against ramularia in barley.

As a new addition to growers crop protection toolkit, Arizona will be ‘crucial this spring, says ADAMA fungicides technical specialist Andy Bailey.

In recent years, the efficacy of some of the principal wheat and barley single-site SDHI, azole and strobilurin fungicides has been eroded by the development of resistant strains.

Advice

The key advice for those controlling fungal diseases such as septoria, ramularia and rhynchosporium, is to keep ahead of the game by ensuring adequate protectant control is achieved. As a multisite inhibitor, folpet works against three biochemical pathways in fungal cells, interfering with spore germination, cell division and mitochondrial energy production, making it less susceptible to resistance compared to single-site actives.

And with chlorothalonil no longer an option for growers, ADAMA says Arizona, powered by MSI Protech technology, remains the most effective multisite fungicide proven to protect and prolong the efficacy and life of single-site chemistries.

In wheat, the continued reduction in the efficacy of triazoles against septoria has been further complicated by the decreasing sensitivity of an increasing number of septoria strains to azoles and SDHIS.

Only the new azole fungicide, Revysol, offers effective curative action but, as a single-site active, this too is at potential risk of resistance and therefore needs to be protected to ensure its long-term efficacy.

Barleys position is slightly more favourable in terms of resistance but the erosion of efficacy of azoles, along with SHDI sensitivity shifts and some resistance to strobilurin chemistry, means diseases such as ramularia and net blotch are becoming increasingly difficult to control, Mr Bailey explains.

For effective long-term protection, application timing is key, as is the array of ingredients used and the rate and frequency at which they are applied, he adds.

Modelling work carried out by Rothamsted Research has shown that when applied in mixture, Arizona can extend the life of azole fungicides significantly.

And a recent ADAS project similarly indicated that partnering Arizona with the SDHI fluxapyroxad significantly extended its in-field efficacy and life expectancy.

ADAMA says this places Arizona as a ‘critical element of spring fungicide programmes, given the multisite is flexible enough to be used at a number of spray timings.

Despite T1 remaining the priority timing for septoria control with a multisite in wheat, in terms of yield response and return on investment, Arizona can also be used at T0 and T2, thereby enabling it to be used as a resistance management tool throughout the season.

Likewise, Arizona is the ideal protectant for barley crops where the key timing for 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.

In barley, to achieve effective control of both diseases a two-spray programme should be considered, Mr Bailey says.

The inclusion of folpet which the Fungicide Resistance Action Group describes as a ‘valuable tool to manage resistance, providing added levels of disease control while protecting the efficacy of at-risk chemistries in disease control programmes is a must from the perspective of resistance management, he says.

But striking the right balance between return on investment and efficacy remains an important factor for growers when looking to achieve sustainable disease control.

Arizona has proven to be a cost-effective addition to spray programmes, boosting cereal yields and providing advanced protection against fungal diseases, says Mr Bailey.

Efficacy

According to an ADAMA trial, Arizona boosted efficacy on septoria and improved efficacy per £/ha spent, demonstrating the cost-effectiveness of applying a multisite in combination with a single-site fungicide, as opposed to the application of a single-site alone (see graph, below).

And with reports of some septoria, yellow rust and mildew present in winter wheat, especially in the earlier September drilled crops, Arizona will be important for the coming season, says Melanie Wardle, ADAMA product manager.

Although recent cold spells did dampen the mildew, this will quickly resurface once conditions turn milder.

In barley, recent rainfall has also encouraged rhynchosporium and net botch development, she adds.

Mr Bailey reminds growers that best results are achieved when Arizona is used as part of an integrated approach to disease management, explaining the selection of cereal varieties with robust disease resistance will become ‘increasingly important as the erosion of curative fungicides continues.

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, Mr Bailey concludes.

What growers need to know:

• Crops: Winter and spring wheat, winter and spring barley and triticale

• Max individual dose: 1.5 litres per hectare

• Max total dose: Three litres per hectare Latest time of application: Before end of heading/inflorescence fully emerged (GS 59)

Wheat recommendations:

• Typically should be applied at a rate of 1.0-1.5 litres per hectare at T1 and T2

• One litre/ha at T0

• Maximum application rate of three litres per hectare per crop

• In high risk situations, three applications should be made at rates of one litre per hectare (T0, T1, T2)