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Tackling potato late blight in 2026: Resistance update & fungicide programme best practice guidance
Craig Chisholm, Field Technical Manager for Fungicides at Corteva Agriscience, and Dr Faye Ritchie, Plant Pathologist at RSK ADAS, discuss the evolving challenges facing potato late blight control in the UK in 2026, and what they mean for fungicide programmes. With fewer tools available and rising pressure from resistant strains, the focus has shifted from individual products to the overall strength and resilience of the fungicide programme.
Watch the video or read on below to find out more.
A changing blight landscape
“The two key challenges are the loss of the key multi-site fungicide Mancozeb and the arrival within the UK population of resistance to multiple modes of action.” Craig Chisholm explains. This evolving resistance highlights the need to treat fungicide inputs as a shared resource, one that must be protected to ensure long-term efficacy.
From product choice to programme strategy
Effective blight control is no longer driven solely by product selection. Instead, success depends on how those products are used together within a well-designed programme. The key principle for 2026 is maintaining the genetic diversity within the p.infestans population by utilising all the modes of action available across the late blight fungicide programme. By avoiding over-reliance on any one chemistry and carefully alternating and mixing modes of action, growers can reduce selection pressure on the pathogen and help preserve the effectiveness of available fungicides.
Building strong foundations
A robust programme starts before fungicides are applied. Cultural control remains a critical first step in reducing overall disease pressure.
This includes:
- Eliminating sources of infection such as volunteers and out grade piles
- Using high-quality seed to minimise the risk of introducing blight into the crop
- Considering variety choice where possible to support disease resilience
Establishing a clean starting point helps reduce early infection risk and sets the foundation for a more effective fungicide strategy.
The importance of early programme design
Getting the programme off to the right start is essential. Begin with a strong early-season approach, by including a curative non-OSBPI partner fungicide, such as Option®, in the first few sprays when the base of the crop is accessible to the fungicide. This helps ensure crops begin clean, and reduces the risk of late blight becoming established. From there, consistency is key. Maintaining a regular spray interval of seven days ensures continuous protection and supports a preventative approach to disease management. Preventative programmes remain significantly more effective than reactive ones, particularly in a season where resistance pressures are increasing.
Managing resistance through diversity
“The challenge now is to mix fungicides with differing modes of action (MoA) at each application timing such that single MoA fungicide products are not applied in isolation, as where you have single site MoA there is a far greater risk of developing resistance.” Faye Ritchie outlines.
To minimise resistance risk:
- Use mixtures of active ingredients with different modes of action
- Alternate chemistry between applications
- Avoid repeated exposure of the pathogen to the same mode of action
This approach helps reduce selection pressure and slows the development of resistant strains, supporting the longevity of key fungicide actives.
Stewardship and best practice
Stewardship guidance plays a vital role in ensuring fungicide performance is maintained across the industry. Following best practice recommendations, from Corteva Agriscience as well as advisory bodies and other manufacturers, utilising a mixing and alternating strategy, along with limiting the frequency of key actives and avoiding back-to-back applications of similar chemistry, supports both resistance management and programme effectiveness. Industry initiatives, including monitoring programmes such as Fight Against Blight, are essential in tracking changes within the pathogen population and informing future guidance.
A programme-focused approach for 2026
As the blight landscape continues to evolve, the most successful strategies will be those built around strong, disciplined programme design.
The core principles remain clear:
- Start clean with effective cultural control
- Build a programme that prioritises diversity
- Maintain a preventative approach with consistent timing
- Follow stewardship guidance to protect key chemistries
By focusing on the overall programme rather than individual applications, growers can better manage resistance risk and maintain reliable late blight control throughout the season.
To earn CPD points, visit the Zorvec active hub to watch the full spring technical update for potatoes from Corteva.
To find out more about the Corteva solutions available to potato growers visit the dedicated potato hub.
Tackling Potato Late Blight in 2026: Resistance Update & Fungicide Programme Best Practice Guidance
Tackling Potato Late Blight in 2026: Resistance Update & Fungicide Programme Best Practice Guidance
About Corteva
Corteva, Inc. is a publicly traded, global pure-play agriculture company that provides farmers around the world with the most complete portfolio in the industry - including a balanced and diverse mix of seed, crop protection and digital solutions focused on maximising productivity to enhance yield and profitability. With some of the most recognised brands in agriculture and an industry-leading product and technology pipeline well positioned to drive growth, the company is committed to working with stakeholders throughout the food system as it fulfils its promise to enrich the lives of those who produce and those who consume, ensuring progress for generations to come. Corteva Agriscience became an independent public company on June 1, 2019, and was previously the Agriculture Division of DowDuPont. More information can be found at https://www.corteva.com/uk
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