Trials underline benefit of cereal disease control

Timing and spray quantity are key

Mixing a multi-site fungicide with single-site active ingredients can significantly improve wheat and barley yields, suggest the latest trials.

Including Arizona (500g/l folpet) as a partner product to other single site fungicides  can pay for itself by a factor of four to one – and boost winter wheat yields by an average of 0.3t/ha, according to six years of data.

This yield benefit is achieved by enabling crops to get ahead and stay ahead of disease infections, explains Andy Bailey, fungicide specialist with crop protection specialists Adama.

“Putting Arizona to work alongside single site fungicides at key stages in the growing cycle helps crops to retain green leaf area for longer which in turn enables plants to capture more sunlight and produce a better yield.”

‘Crucial role’

“At an ex-farm wheat price of £200/tonne, a yield uplift of 0.3t/ha is equivalent to an additional £60 of income per hectare,” he adds. “That equates to a return of up to £4 for every £1 spent on folpet.”

The addition of folpet plays a crucial role in disease resistance management, says Mr Bailey. This is because it helps crops outgrow the disease threat earlier while slowing the rate at which resistance develops.

“The erosion of the efficacy of the current arsenal of single site fungicides means growers can no longer rely on the curative activity of these actives as a get out of jail free card once infections have taken hold.”

“Instead, it is vital to get ahead of diseases by applying early season protection and to stay ahead by making subsequent treatments as the crop develops and each ensuing leaf emerges,” adds Mr Bailey.

To combat septoria in winter wheat, the critical timing for the inclusion of Arizona is at T1 when it delivers an average yield uplift of 0.21t/ha compared to 0.14t/ha at T2 only.

But Mr Bailey suggests that a programmed approach – with inclusions at T1 and T2 – will provide growers with the best results, contributing to an average yield improvement of 0.35t/ha.

Arizona can also be used at T0 in high-risk situations, for example where a disease susceptible variety has been drilled early and is growing in persistently damp conditions.

“Timing of application is dependent on a range of factors including the variety being grown, drilling date, location, prevailing weather conditions, previous fungicide applications, ongoing disease pressure and the partner products being used.

Improved persistence

As a general rule, Arizona should be used at least once during the season. But evidence from six years of testing and 272 field-based comparisons suggest that including it twice will provide improved persistence and better long-term protection.

Application rate also has an impact on yield benefit with two treatments of 1 litre/ha at T1 and T2 resulting in an average yield increase of 0.32t/ha. Similarly, three treatments of 1 litre/ha at T0, T1 and T2 improves yield by an average of 0.39t/ha. In contrast, two applications of 1.5l/ha at T1 and T2 saw an average yield response to 0.41t/ha.

“A tiered approach gives the best results, with trials showing that the more is applied, the greater the benefit,” says Mr Bailey

“Two applications of Arizona will therefore provide better protection and a greater yield benefit than a single treatment, but growers can maximise the benefit by applying the maximum three litres per crop either by splitting equally across two or three applications. Either way, Arizona more than pays for itself.”

Protecting barley

Arizona offers similar yield protection and return on investment benefits when used in barley programmes aimed at preventing and controlling ramularia, net blotch and rhynchosporium.

“In winter barley the key timing to use Arizona to control ramularia is at T2, but it can also be used at T1 to boost disease control and to help with resistance management,” says Mr Bailey.

“The T2 timing is also key for protecting against ramularia, with a two-spray approach (for example at T1 and T2) giving the best results, particularly where disease pressure builds early in wet conditions.

Depending on the circumstances, the inclusion of Arizona alongside single site actives can provide a positive yield response in excess of 0.3t/ha, with some protocols seeing yields increase by as much as 1.0t/ha.”

Managing resistance

In scenarios where resistance management is the key driver, Andy explains that it is advisable to maximise the dose of the active ingredient with the lowest risk of resistance.

“In other words, use a full rate dose of Arizona to protect ‘at risk’ single site modes of action, and, where disease pressure allows, reduce the selection pressure exerted on single site fungicides by applying them at an appropriate dose in mixture.

“That it also prolongs the effective life of those fungicides already at risk of resistance is the icing on the cake and an added reason for growers to put it to work alongside their usual array of single site actives.”