Late Blight Updates
February 2026
Independent monitoring by the Fight Against Blight initiative has confirmed a case of EU_43 blight in the UK.
The isolate case was located from a volunteer potato plant in Suffolk in November last year.
For the coming season experts recommend continuing to use the full range of blight control products, in mix with alternative mode-of-action fungicides.
Experience of potato growers in Denmark indicates the EU_43 blight strain can be effectively managed with a mix and alternation strategy, with the strain’s impact reduced year-on-year.
Blight – the greatest threat to potato crops
Potato late blight (Phytophthora infestans) continues to create the greatest challenge for potato growers and agronomists. Blight outbreaks can quickly devastate entire fields, leading to significant yield losses and widespread tuber blight infection.
Favoured by warmer and wetter conditions associated with climate change, issues have been getting progressively more difficult. Blight resistant potato varieties currently offer little or no respite.
New Syngenta R&D for blight protection products and technical support ensures growers and agronomists are best placed to succeed in the fight against blight.
When dealing with blight-affected potato crops,
it’s crucial to act quickly and decisively.
Adapting to the threat of new blight strains
The ongoing evolution of new, more aggressive, blight strains poses ever greater threats to blight management strategies.
Independent monitoring by the Fight Against Blight initiative has confirmed the UK’s first recorded instance of EU_43 blight in Suffolk in November 2025, sampled from a volunteer potato plant post harvest.
Despite the risk of resistance to CAA and BSBPI chemistry with EU_43 blight strains, it is important to acknowledge that growers and agronomists should still utilise these valuable fungicide groups this season and manage blight populations through an effective strategy.
It is well documented that compromised actives can still be used effectively in a good mixing and alternating approach, to reduce the outbreaks of resistant strains.
Top tips for managing late blight in potatoes:
- Maintain mandipropramid, e.g. REVUS®, efficacy by mixing with a different mode of action* blight fungicide.
- Apply mandipropamid, or other CAA fungicides, preferably in a preventative manner.
- FRAC guidance states not to apply mandipropamid, or other CAA fungicides, in more than two consecutive applications. To further strengthen the CAA anti-resistance strategy, use mandipropamid in alternation with fungicides of a different mode of action.
- Up to six applications of CAA containing fungicides can be applied, making up no more than 50% of the intended total number of sprays.
- Good agricultural practices must be considered to reduce source of inoculum, disease pressure and resistance risk, e.g. consider planting resistant varieties and refer to disease prediction models.
*An effective partner for REVUS® is one that provides satisfactory disease control when used alone at the mixture rate.
Effective active ingredient mix partners for REVUS®
| FRAC Group | FRAC Group number | Active ingredient mix partner | Product example with active ingredient | Comments and restrictions |
|---|---|---|---|---|
| Quinone outside inhibitor (QiI) | 21 | amisulbrom, cyazofamid | Shinkon | No more than 3 consecutive QiI products to be applied Not more than 50% of intended programme |
| Carboxylic acid amides (CAA) | 40 | mandipropamid | REVUS® | No more than 2 consecutive sprays Not more than 50% of intended programme Resistance to EU_43_A1 (not found in UK) |
| Oxysterol binding protein inhibition (OSBPI) | 49 | oxathiapiprolin | Zorvec Enicade | Up to 3 applications Not more than 20% of intended programme |
| Carbamates | 28 | propamocarb | Raport | Up to 6 applications |
| Benzamides | 43 | fluopicolide | Not applicable | Co-formulated with propamocarb Maximum number of sprays is 4 at full dose No more than three consecutive sprays |
| Quinone outside inhibitor (QoSI) | 45 | ametoctradin | Enervin | Up to 4 applications of any one product containing ametoctradin No more than 3 consecutive sprays |
| Uncouplers of oxidative phosphorylation | 29 | fluazinam | Shirlan | Up to 10 applications Resistance known within UK blight population e.g. EU_33_A2 & EU_37_A2 |
| Cymoxanil | 27 | cymoxanil | Sipcam C50 WG | Up to 4 applications If blight strains resistant to CAA chemistry are discovered in the UK through the Fight Against Blight programme, mixtures containing Cymoxanil must be combined with another effective active ingredient against late blight. Should only be used in mix with another effective active ingredient against late blight. |
| Metalaxyl-M | 4 | metalaxyl-M | FUBOL®Gold | Up to 3 applications Resistance – EU_13_A2 FUBOL®Gold contains mancozeb, see notes on withdrawal period in the box below. |
Control blight with...
Reduce spray drift to tackle blight: A troubleshooting guide
Learn essential strategies for minimising spray drift during potato blight treatments, from optimal weather conditions to proper equipment setup. Discover how combining the right nozzle technology, like 3D Ninety, with correct application techniques ensures effective crop protection while reducing environmental impact.
Blight Forecasting
Syngenta’s industry leading BlightCast gives growers and agronomists up to 7 days advanced warning of conditions conducive to blight disease infection and development. This invaluable time window allows for proactive measures to fine tune blight protection strategies.
Access BlightCast for free as part of the Spray Assist app, with a section specifically dedicated to potato and sugar beet growers.
Download the Spray Assist app for free
Stay informed, stay prepared, and stay ahead with BlightCast, Syngenta's industry-leading forecasting tool!
Ask the expert: What’s the best way to control blight?
Discover how late blight continues to threaten potato crops through evolving genotypes and resistance challenges, while learning about modern control strategies. Expert insights from Andy Cunningham explain how combining fungicide programs with cultural practices helps protect potato yields from this historically devastating disease.
FAQ
Strengthen Blight Protection With ICM
A robust fungicide strategy is the cornerstone of protection against blight. Developing an integrated crop management (ICM) approach adds greater reliability and resilience.
By utilising a full range of cultural practices and improving plant health, it also provides further protection of existing chemistry against evolving blight strains.
Application On Target Every Time
Syngenta application technology has revolutionised potato crop treatments, ensuring accurate coverage to enhance performance of every application.
Our exciting new R&D has clearly demonstrated the Syngenta 3D ninety nozzle gives the optimum results for all blight and foliar applications in potatoes, to deliver every product in the right place, at the right time.
Supporting Fight Against Blight
Syngenta is proud to continue our ongoing sponsorship of the Fight Against Blight programme, managed by the James Hutton Institute.
Monitoring blight populations and analysing the genetic make-up of any disease outbreaks is crucial for effective product selection and future control strategies.
We recommend the Syngenta 3D ninety nozzle for blight sprays. The engineered droplet spectrum and specific angle of delivery enables spray throughout the dense crop of potatoes, effectively protecting lower leaves and stems against potato late blight infection. The larger droplets penetrate crop canopy with greater momentum, while fine droplets are more prone to drift. Read the full article.