Arable
Prothioconazole options pitched together in pot trial tests The adage ‘pay your money and take your choice’ is apt when it comes to branded products versus genetics. For farmers, trying to work out what is best is tricky, cost savings having to be pitched against reliability and performance. Generic manufacturers often claim that off-patent products perform as well as original formulated brands. The chemical brands counter that, for actives to work to their optimum, they have to be supported by an appropriate formulation – something very difficult to achieve. Convinced about the quality of its prothioconazole formulations, Bayer arranged for Nottingham University to undertake some tests. According to Bayer, the findings do suggest that the attractive price proposition of generics could be lost through inconsistent field performance or higher rates being needed. Bayer’s Greg Hanna says that, although generic prothioconazole performs well, it isn’t quite the ‘real deal’, and work at Nottingham University suggests he may have a point, Bayer reckons. Septoria and yellow rust pot trials conducted in 2021 compared 16 different products and mixtures at various rates to deliver the same amount of prothioconazole, tebuconazole or both. It showed consistent improvements in disease control for Proline (prothioconazole) and Folicur (tebuconazole) over generic prothioconazole and tebuconazole alternatives, and Bayer’s co-form of both (Prosaro) over mixed straights. Regardless of the rate, disease, or protective and curative situations, the branded products were more efficacious, according to the trials. University associate professor Stephen Rossall (pictured right), who conducted the research, feels this has to be down to formulation. “We specifically developed the trial so that the amount of active ingredient was the same for all products and mixtures. I assume with the Bayer branded products, the active is getting into the plant and pathogen more effectively. This would particularly explain the difference in curative performance.”
The trials were specifically developed to look at disease control and, being under glass, no environmental benefits could be explored. But Prof. Rossall wonders if the formulation is benefiting the movement of actives, is it helping protect them too? “This was not part of our research, but formulation technology might be improving UV protection or accelerate rainfastness,” he suggests. Mr Hanna says the gap in both protective and curative septoria performance is a strong argument for relying on branded products. “At the 2⁄3 rate, more akin to what occurs in the field, there is a 20-point advantage in septoria control from Proline [compared to a generic product]. That gap was retained when applied curatively – applications made five days after inoculation. Yellow rust trials also highlight differences in protective and curative performance. The performance gap is smaller, but differences remain, he notes. Similar results were seen with Prosaro – a formulation of both prothioconazole and tebuconazole – versus a mix of generic prothioconazole and tebuconazole.
Higher rates required? He adds that to achieve the same level of performance generic rates might need to be higher, possibly offsetting any potential price advantage. The second argument for Bayer formulated fungicides is that he believes there is a link between formulation and field reliability. Mr Hanna points to Bayer work at its Monheim R&D centre, exposing fungicides to challenging storage and transport conditions. Some generic fungicides were found to separate when subjected to high temperatures. “Fungicides are often transported
long distances and stored for long periods; again the formulation needs to protect against temperature fluctuations and movement. “Some of the first generic tebuconazole formulations proved very unreliable, resulting in sprayer blockages through crystallisation. These appear to be rectified but it was no fun for those with a blocked sprayer at the time. We’ve also seen growers switch back to the original glyphosate formulation due to performance issues,” he notes.
Recipe just as important In Mr Hanna’s view, the recipe is as important as the active or actives. “It’s the actives that do the work, but you need to get them there – and that is where formulation comes in. Whether it be Proline, Prosaro or Ascra (prothioconazole + bixafen + fluopyram), there is a very carefully selected blend of wetters, stickers and emulsifiers to ensure the perfect leaf adhesion and penetration of plant tissues. That blend is carefully guarded by us and, whilst the ingredients can be copied, the recipe is very difficult to reliably replicate.” Mr Hanna points out that as formulation advances occur, these are integrated into the Bayer product range. “Our Proline and Xpro formulations include a specialist amide fatty acid that plasticises the cuticle and a castor oil emulsifier to optimise droplet size and spread.” Mr Hanna says, ultimately, growers have to weigh up the ‘risk and reward’ for themselves. “Of course, generics come with a cost benefit, but that usually comes with a greater degree of risk. That could be slightly reduced disease efficacy or reliability in the field. “Also, you might lose some of those added value extras. An azole + SDHI mix should offer good disease control but it might not have the rainfastness of a product like Ascra. Work at SSAU has highlighted how quickly Ascra droplets adhere and spread across the leaf surface. “I am not aware of any Proline or Xpro fungicide product failures for more than 12 years. That is what you’re paying for – optimum performance, but also reliability and consistency over a range of conditions,” he concludes. FG April 2022 www.farmersguide.co.uk 17
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