How can variety choice reduce reliance on cereal fungicides?

Production costs, along with efficacy and environmental concerns, have increased the appetite for more and better quality information on the potential of non-chemical control of cereal diseases. Fiona Geary explores the latest research, including how it has inspired activity in our Farm Excellence network.

Pinpointing the economic value of cultural control has always been a particularly sticky wicket.  This is why we have invested in a five-year project to establish how best to combine agronomy, variety and chemistry in a disease management programme.

With a focus on wheat foliar disease number one – septoria tritici – the integrated pest management (IPM) project puts disease resistant varieties at the foundation of control and looks at the interaction with other key aspects, such as sowing date.

The work has inspired activity in our Farm Excellence network too, with a focus on how a resistant variety can change fungicide use – and if it is actually an economically viable option.

Treating the crop in response to conditions at the Strategic Cereal Farm West

Looking at the effect of a reduced-input regime on cost of production, Rob Fox hosted a split-field trial with a winter wheat crop for harvest 2019 at the Strategic Cereal Farm West. The variety Graham was established using deep tine to 8 inches, discs, drill and roll. Half of the field contained Rob’s farm standard crop, using dressed seed with insecticides and fungicides applied as normal. The other half of the field contained untreated seed, with the treatment programme developed in response to disease and pest pressure.

The assessments done on the field showed no statistically significant difference in yield or disease observations between the farm standard and low-input treatments. No stem diseases were observed and foliar disease levels were low in both treatments. Taking into consideration differing seed treatments, energy costs, fungicide spend and yield,  the cost of production differed from £86/t (£954/ha) for the farm standard treatment and £84/t (£914/ha) in the low-input programme. Full results can be found here.

Trialling high, medium and low-input strategies at the Strategic Cereal Farm East

Similarly, at the Strategic Cereal Farm East, Brian Barker looked into impact of reducing fungicide applications on varieties with different Recommended List resistance ratings. In 2018–19, five winter wheat varieties (Siskin, Shabras, Graham, Santiago and Silverstone) were grown under high, medium and low-input regimes. The results from harvest 2019 showed that growing more resistant varieties with low fungicide inputs gave the best net margin. However, this was a single year with moderate disease pressure.

In harvest year 2020, the trial was repeated in the same field with mostly the same varieties (Silverstone was replaced with Crispin). The tramline trial was replicated twice and the fungicide programme was decided upon as the season progressed, reflecting current weather and disease assessments. The trial showed that there was a minimal response to increasing fungicide spend on resistant varieties. The medium-input trial gave a mean yield of 6t/ha but it was the low-input regimes, with a mean yield of 6.2t/ha, that showed the best net margins. Even on the susceptible varieties (Santiago and Crispin), where the higher yields were seen on the high-input regime (mean of 6.9t/ha), the net margins were similar to the low inputs. Crispin grown with high inputs had the same cost of production as Siskin’s low-input result, both costing £129/t (excluding rent and finance). Full results from the harvest 2020 trial can be found here.

Competition for the best margin in the Fungicide challenge

Farmer groups in the East Anglia, South West, West and Wales regions competed to develop a fungicide strategy to maximise gross margin, rather than focusing on yield alone. In each of the three regions, a replicated plot trial was hosted by one of the farmers and managed by ADAS. Each person in the group then decided the fungicide programme for their plot depending on the crop update shared by their ADAS trial manager. All other inputs and management stayed the same.

Across all of the entrants, the best margins were achieved with low-to-moderate fungicide inputs, both by product and number of applications. Septoria was not a major problem in spring 2020, so only a very small yield benefit was seen in those plots where septoria was controlled. Ultimately, those who were brave enough to reduce their fungicide applications came out on top.

What this means for you

By responding to disease pressure based on varietal resistance, opportunities can be taken to reduce inputs and save cost, improving net margins and reducing the risk of resistance developing in fungicides.

Choosing a variety with a suitable resistance rating, using monitoring tools, assessing the crop and matching inputs to the conditions is a good way of preventing, detecting and controlling disease. Planning ahead is vital to growing in an economically and environmentally sustainable way.

Tools for planning ahead

• Use the AHDB Recommended Lists to choose varieties with resistance traits
• Use Farmbench to get a handle on your cost of production and see how varied fungicide spend can affect your business
• Understand the life cycle of the disease, risk factors and control options by using the Wheat and barley disease management guide and oilseed rape disease management guidance
• Use the WeatherHub and related weather tools to help predict risk and manage the crop accordingly
• Check your crop to decide when to take action – videos like How to score disease symptoms in wheat can help gauge the level of infection