As expectations on spray performance increase, attention is shifting from what goes in the tank to how well it actually works. CPM explores why adjuvants could be an overlooked opportunity and the agronomic benefits they can offer.
“With the current price of fungicides, it’s more important than ever to make them work.” PAUL DUNHAM
By Charlotte Cunningham
There’s no shortage of scrutiny on cereal fungicide programmes. From product choice to timing and dose rates, decisions are weighed carefully often down to the finest detail. But while plenty of attention is paid to what goes into the tank, sometimes less is given to how well it actually performs once it leaves the nozzle and reaches the leaf.
That’s where adjuvants come in – or, in many cases, don’t. Despite sitting at the intersection of spray quality, coverage and efficacy, adjuvants remain absent from a surprising number of programmes.
Arguably not through a conscious decision to leave them out, but more often because their role isn’t fully understood. And yet, in an era where every input has to justify its place, it raises a timely question: if you’re not using an adjuvant, what are you potentially missing?
Cereal fungicide programmes are, at their core, about precision. Each timing is designed to protect a specific layer of the canopy, based on its contribution to final yield. “The flag leaf accounts for around 40% of yield,” highlights Oliver Johnson, commercial technical manager at Nichino. “So it’s no surprise that the T2 application tends to carry the greatest investment. However, the second leaf down still contributes around 20%, and that’s often overlooked.”
That second leaf is rarely targeted directly, he adds. T1 is aimed at leaf three while T2 focuses on the flag leaf, so unless a T1.5 is brought into the programme, that middle layer can go largely unprotected. “Yet when you combine the contribution of the flag leaf and leaf two, you’re looking at 60% of final yield,” says Oliver. “So anything that improves how effectively we protect both of those leaves has a significant impact on return.”
Of course, applying a fungicide to a crop is one thing, but getting it to the correct place in the right quantity is another entirely.
Spray quality sits at the centre of that challenge. Fine droplets improve coverage but are prone to drift; coarser droplets travel further into the canopy but reduce the number of contact points on the leaf. “There’s always that compromise,” suggests Oliver. “You want droplets to penetrate deeper into the crop but you also require them to spread and cover the leaf effectively.”
As crops move through stem extension and into flag leaf emergence, that challenge only intensifies, he adds. Denser canopies, layered leaf structures and narrowing spray windows all increase the risk that parts of the crop receive less protection than intended.
This is often the point where adjuvants come into sharper focus – not as an add-on, but as a way of improving how the application performs in practice. In simple terms, their role is to bridge the gap between what leaves the nozzle and what the crop actually receives – influencing droplet size, movement, retention and uptake.
For Paul Dunham, agronomist at Agrii, that’s where their value becomes most apparent. “My preferred placement for an adjuvant is where I want to penetrate fungicides into the crop and get good coverage,” he explains. “So typically, that’s T1 and T2, or in particularly dense crops.”
Without that intervention, parts of the canopy – particularly those middle leaves – can easily be left short of protection, not because of poor product choice or timing, but simply because the spray hasn’t reached where it needs to, he warns.
Adjuvants are designed to address exactly that problem, influencing how spray behaves from tank to target. One example which has been heavily proven in the field is Kantor, an adjuvant from Nichino based on a patented alkoxylated triglyceride chemistry. Unlike traditional oils or wetter-spreaders, it works across multiple stages of the spray process – from stabilising the tank mix to improving how droplets interact with the crop.
At the point of application, its primary role is to refine droplet behaviour. “Kantor reduces the number of very fine and very coarse droplets,” explains Oliver. “So you get a more uniform spray pattern which improves both canopy penetration and coverage.”
But its effect doesn’t stop there, he adds. By reducing surface tension, it allows droplets to spread more effectively across the leaf, increasing contact area and retention. And, because its chemistry supports improved interaction with the leaf surface, it helps to maximise the uptake of active ingredients. “You’re not just getting product onto the leaf, you’re helping it get into the leaf. That’s particularly important with systemic fungicides,” comments Oliver.
For Paul, that combination is key. “Kantor decreases the surface tension so droplets adhere better, but also improves penetration into the crop,” he explains. “So you’re getting both coverage and movement into the plant.”
The practical implication of that is simple – better protection of the leaves that drive yield. At T2, attention naturally focuses on the flag leaf, but as Oliver points out, the second leaf below contributes a significant proportion of yield and often relies on indirect coverage. “That leaf might not have received a fungicide for several weeks,” he says. “So ensuring droplets can reach it and perform once they get there is critical.”
By improving both droplet trajectory and spread, adjuvants can help to bridge that gap, he suggests. “You can maintain a medium spray quality and still achieve penetration deeper into the canopy. That’s where products like Kantor come into their own.”
Arguably, a common assumption is that modern fungicides, particularly premium formulations, already contain sufficient adjuvant technology; field experience suggests otherwise. “There’s actually a bigger benefit realised with adjuvants when you’re using high-value chemistry,” raises Stuart McDowall, Agrii agronomist in Lincolnshire. “This is because you’re trying to eke out every percentage of performance.”
Even with well-formulated products, in-can adjuvants are fixed at a rate determined by product dose rather than water volume or application conditions. “Tank-mix adjuvants give you flexibility,” explains Oliver. “You can tailor the rate to suit the situation – whether that’s water volume, crop density or spray quality.”
For Stuart, that flexibility translates directly into performance. “Even with premium fungicides, adding something like Kantor gives you a benefit,” he says. “As for generics, it can be even more important.”
With marginal conditions and short weather windows becoming the norm, few applications today involve a single product. Tank mixes often include multiple fungicides, PGRs, micronutrients and more – each bringing its own formulation challenges. “It’s not uncommon to have eight products in the tank,” highlights Stuart. “That’s where things can start to go wrong.”
Such compatibility issues can reduce efficacy, block filters and create inconsistency in application. “Kantor acts as a compatibility aid,” he adds. “It helps everything to mix properly and stay stable, which gives you confidence that what you’re applying is what you think you’re applying.”
This is particularly relevant in less-than-ideal conditions, says Paul. “In cold water or hard water, some products don’t mix as well. Having that buffering and compatibility effect makes a significant difference.”
Kantor also buffers spray solution pH, helping to protect active ingredients from degradation in alkaline conditions – something that can otherwise reduce efficacy before the spray even reaches the crop. “It’s easy to overlook what’s happening in the tank,” notes Oliver. “But if the chemistry isn’t stable, you’re already losing performance before you start.”
Water quality is often an unseen variable, but is another factor which can have a measurable impact on chemistry performance. “We’re in a hard water area across all our farms and that can bind up active ingredients and reduce performance,” points out Stuart.
Glyphosate is a well-known example, but the principle extends to other products too. “We’ve seen efficacy drop from the moment products hit hard water,” adds Paul. “So buffering that water is important.”
That sensitivity can have practical implications in the field, particularly where resistance pressure is building. As Oliver points out, glyphosate is among the most pH-sensitive actives, meaning performance can quickly be compromised if conditions aren’t right. With ryegrass increasingly challenging control strategies, ensuring the dose is appropriate for weed size – and that it’s able to function as the manufacturer intended – becomes critical.
However, by conditioning water and stabilising pH, adjuvants can help to preserve the integrity of the chemistry – ensuring it performs as intended.
Another area where adjuvants come into their own is combatting inclement conditions. Stuart reminds that because application conditions are rarely perfect – wind, temperature and rainfall all influence how sprays behave – increasingly narrow weather windows add further pressure. “You can’t always wait for ideal conditions,” he says. “So anything that reduces drift or improves rainfastness gives you more flexibility.”
Kantor’s ability to reduce fine droplets helps minimise drift, while improved retention supports rainfastness. But as Oliver points out, drift isn’t just a function of windspeed – it’s also influenced by how long droplets remain airborne.
By producing a more consistent droplet spectrum and encouraging droplets to settle and adhere more quickly, products like Kantor can help to reduce time aloft, meaning more of the spray reaches its intended target. Stuart concurs: “I’ve had growers ring me up asking for it because it’s wind and they want that extra reassurance.”
For many, that reassurance translates into operational efficiency – spraying crops when required, rather than when conditions are perfect.
While efficacy is often the headline, crop safety is another key consideration of adjuvants, particularly with complex mixes or more aggressive chemistry, suggests Stuart. “I use it with harsher herbicides like Atlantis (mesosulfuron+ iodosulfuron). It safens the mix and reduces the risk of scorch.”
In one case, the difference was stark, he recalls. “We had a field where part was treated with an adjuvant and part wasn’t. Where we hadn’t used it, the crop was yellow; where we had, it was fine and we had better weed control as well.”
Ultimately, every addition to the tank has to justify its cost and adjuvants are no exception. However, their value is often underestimated because their effect is less visible than a product switch or rate change, believes Oliver. “Kantor has consistently delivered around a 0.3t/ha yield increase across trials, and that’s across different seasons and programmes,” he says.
For Paul, the logic is straightforward. “With the current price of fungicides, it’s more important than ever to make them work. If an adjuvant helps you do that, it’s an easy decision.”
And for Stuart, the return isn’t just about yield. “It’s about consistency,” he says. “Knowing that your spray is doing what it should, across the whole canopy, in whatever conditions you’re dealing with.”
For many, adjuvants have historically been seen as an optional extra, something to consider when conditions are difficult or where specific challenges arise. But increasingly, that thinking is changing.
As programmes become more complex, margins tighter and expectations of performance higher, attention is shifting towards the efficiency of the whole system, rather than just the individual components within it.
“Adjuvants are one of the least understood areas,” concludes Oliver. “But they can rival any fungicide in terms of what they bring to the tank and final yield.”
This article was taken from the latest issue of CPM. Read the article in full here.
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