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Pushing fungicide performance: The role of adjuvants in increasing efficacy

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With fungicide resistance on the increase, we look at the role of adjuvants in increasing efficacy.

While SDHI/azole mixtures have proven effective in controlling septoria in cereals, AHDB fungicide performance data shows there has been a slide in sensitivity to SDHIs and azole chemistry.


This together with the EU’s recent decision to ban fungicide chlorothalonil means resistance poses a significant threat to the ongoing performance of fungicides in wheat and barley, and places even greater pressure on growers’ cost of production.


Using all available tools to protect chemistry and optimise efficacy and yield is becoming ever more critical, believes Stuart Sutherland, Interagro technical manager, and this is where a suitable adjuvant can be extremely valuable.


Often overlooked, the right adjuvant can enhance delivery, uptake and improve performance of fungicides. This reduces disease inoculum, increases green leaf area and can increase overall yield and profitability.


Mr Sutherland says: “During fungicide application the aim is to get as much active ingredient inside leaves as possible. The surface area is large and it all needs protecting.




“While multi-sites, such as chlorothalonil and folpet, act as a protectant, they do not move on the leaf. This means they can only protect the portion of the leaf they actually cover.


“If the base of the leaf does not receive adequate coverage, the fungicide will not be able to move downwards, leaving that part of the leaf either completely unprotected or having received a sub-lethal dose of the active ingredient.”


Achieving good deposition of the fungicide active ingredient on the leaf, which can then move inside, is therefore an essential requirement for effective disease control, he says. However, fungicide efficacy can be compromised at each step of the delivery process.


  • ONE: Spray tank issues.
    Fungicides (and other pesticides) can breakdown in high pH water and complex tank mixtures can lead to antagonism, as we typically see with prothioconazole + chlorothalonil in curative situations.

  • TWO: Spraying issues.
    Spray coverage can be compromised by drift, reducing the dose and coverage on the crop, which can allow disease to establish. Drift reducing nozzles will reduce drift but they also reduce coverage.

  • THREE: Leaf issues.
    When the fungicide is applied to the crop it must be retained on leaves and then spread out to protect it. Critically, the fungicide active ingredients must be able to penetrate through the waxy leaf cuticle of the leaf to their site of action insider the leaf to protect it and control the established disease. The leaf cuticle is the biggest barrier to crop protection products.

Interagro’s adjuvants Arma and Kantor buffer the tank mixes down to a pH of 6 which help keeps crop protection products more stable in water. Kantor will also aid compatibility and reduce drift.


Both Arma and Kantor improve retention/spreading and, importantly, enhance uptake into the leaf, although how they do this is different. Arma disrupts the waxy cuticle on the leaf surface, whereas Kantor packs three times as many molecules at the leaf surface compared to a typical adjuvant, increasing the diffusion rate into the leaf.



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Prothioconazole-based mixes will benefit in particular as it is a large molecule which needs to be converted to desthioconazole inside the leaf for it to be activated.


The faster it enters the plant, the faster it starts working. Extensive trials over the past seven years have also shown that where Kantor is added to prothioconazole-based sprays with chlorothalonil, antagonism is reduced and yield is improved, says Mr Sutherland.


With the loss of crop protection products, or reductions in permitted rates, as well as the resistance issues, Mr Sutherland sees demand for adjuvants rising.


He says: “All these issues can be alleviated by using a suitable adjuvant at T0-T3 to make the fungicide work better.”


It also makes sense from a resistance management perspective.



Managing fungicide resistance

A good fungicide anti-resistance strategy should:

  • Exploit all practical, non-chemical control methods to reduce disease risk and slow epidemic development
  • Limit the time over which the pathogen population is exposed to the fungicide
  • Use effective mixtures and alternate fungicides with different modes of action
  • Use the minimum dose required to control target pathogens

Source: Fungicide Futures



Results: Effect of Kantor on winter barley trials

Over six years of Interagro trials involving 44 comparisons, average yield benefit through using Kantor in winter wheat across all timings was 0.28 tonnes/hectare.



An adjuvant designed to optimise each step of the spray delivery process of fungicides, herbicides and PGRs, from buffering, compatibility and placement, to penetration into the leaf, leading to higher efficacy.

Features and value in use:

  • Buffering to pH6 – increases active ingredient uptake at high pH
  • Compatibility – reduces antagonism and ensures all actives in the mix are available for uptake into leaves
  • Anti-drift – increases dose and coverage on all plants for best control/protection
  • Retention & spreading – protection of the whole leaf
  • Penetration – faster uptake into the leaf increases speed of disease control/overall efficacy


More than 60 approved label crops including winter and spring cereals, broad beans, combining and vining peas, field beans, OSR, linseed, sugar beet, forage maize and potatoes.


0.15% of final spray volume.

Mixing order: 1. Kantor; 2. Crop protection product.

Key situations in which to use Kantor

  • Regions with high pH water
  • Tank mixes hard to keep in solution or pose antagonism risk e.g. prothioconazole mixtures with chlorothalonil
  • Situations where drift will reduce coverage
  • Pesticides impacted by cold weather e.g. CCC, SUs
  • Target is waxy, hairy/hard to coat e.g. barley, brome, ear
  • Delayed applications e.g. curative sprays
  • Actives metabolically activated – trinexapac, prothioconazole
  • Resistance management

Source: Interagro

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