‘The cost of being late’: Ecuador’s zebra chip warning to the global potato industry

What Ecuador’s experience with zebra chip can teach the global potato industry about preparedness, diagnosis and the human cost of being late.

By Lukie Pieterse, Editor/Publisher of Potato News Today

On 21 August, a European potato research project published an account from Ecuador that deserves attention well beyond Europe. It was not a story about a laboratory breakthrough or a new product ready for sale. It was a report from people who have already lived through the arrival of a difficult disease complex – and who are now helping countries where the principal threat is still absent prepare for it.

The project is PATAFEST, a €6.1 million Horizon Europe initiative involving 18 partners and running from June 2023 to May 2027. Its work ranges from disease-resistant germplasm and biological crop protection to camera-based sensors, predictive models and storage treatments. The immediate focus is Candidatus Liberibacter solanacearum – usually shortened to CLso or Lso – and the potato psyllid, Bactericera cockerelli, associated with zebra chip disease.

The newest account comes from Ecuador’s National Institute of Agricultural Research, INIAP. Researcher Xavier Cuesta told the project that cultivated potato area in affected parts of the country has declined by a documented 75% compared with the years before the disease was identified. He said insecticide applications had increased by between 50% and more than 100% in some areas.

Those are INIAP’s reported figures, not a new national statistical release independently audited for this article, and they should be read accordingly. Even with that caution, the experience behind them is too important to dismiss. It shows what can happen when diagnosis lags, extension messages travel unevenly and growers are forced to manage a fast-moving biological problem before science has supplied a reliable playbook.

A warning from the Andes

Ecuador is not merely another trial location in an international project. The Andes are the potato’s centre of origin, home to an extraordinary reservoir of cultivated and wild diversity. INIAP maintains a collection estimated at more than 500 accessions, and its researchers can test European and Ecuadorian material under genuine disease pressure – something that cannot ethically be done in open European fields while the zebra-chip-associated vector and bacterial haplotypes remain absent.

The human setting matters just as much as the biology. Cuesta told PATAFEST that almost 90% of Ecuadorian potato growers farm less than one hectare. Some communities primarily speak Quechua, some growers have limited literacy, and access to digital media and specialist advice is uneven. When the problem first appeared, many farmers did not recognise it early enough to respond. In the information vacuum, some agricultural retailers reportedly offered advice that researchers considered incorrect.

This is where a plant-health story becomes a social story. A new pest does not enter a level landscape. It enters a world of unequal access to laboratories, agronomists, credit, trusted information and alternative land. A large grower may absorb another scouting programme, a change in chemistry or the rejection of part of a crop. For a family cultivating less than a hectare, the same event may alter what is planted next year, whether a child remains in school or whether farming remains possible at all.

Cuesta described the practical effect in a few words: with the new pest, “we had to start over.” That is the sentence the rest of the potato world should remember.

One name, several biological realities

The terminology around CLso is easily oversimplified, and careless reporting can create the false impression that Europe either has zebra chip already or is entirely free of the bacterium. Neither statement is accurate.

CLso consists of genetically distinct haplotypes associated with different plant hosts and psyllid vectors. Haplotypes A, B and F are linked to solanaceous crops and the potato/tomato psyllid B. cockerelli. Together, that pathogen-vector relationship is associated with the classical zebra chip problem encountered in parts of North and Central America, New Zealand and Ecuador.

Europe has recorded other CLso haplotypes, principally C, D and E, in crops such as carrot, celery and other members of the Apiaceae family, carried by different psyllids. The zebra-chip-associated potato psyllid is not established in Europe. EPPO lists it as a serious quarantine concern, and a German pest-risk analysis concluded that the vector and damaging solanaceous haplotypes could establish in Germany and elsewhere in the European Union under suitable conditions.

There have been findings that require careful context. CLso haplotype E was detected in stored potatoes in Spain, for example, but subsequent official surveys reported the organism eradicated from potato production there. That episode is not evidence of an established European zebra chip epidemic. It is evidence that surveillance, diagnosis and precise identification at haplotype level matter.

The distinction may appear technical, but policy rests on it. Quarantine decisions, import requirements, field responses and public communications can all go wrong when a bacterial species is discussed as if every strain, host and vector behaves in the same way.

The defect the processor cannot accept

Zebra chip became notorious because the most commercially damaging symptom may only become unmistakable when a tuber is cut and fried. Infection alters tuber chemistry, producing dark bands or patches in crisps and fries. A crop that appears serviceable in the field can therefore become a processor’s quality failure. Fresh-market yield and appearance can also suffer, but in processing the tolerance for the defect is understandably very low.

The disease is difficult to manage because the bacterium lives in the plant’s phloem and is transmitted during psyllid feeding. Visual symptoms can be confused with other disorders, including phytoplasma-related purple top and damage caused by psyllid feeding alone. Ecuadorian researchers report mixed infections in the field, making image-based diagnosis particularly demanding. A photograph may be useful for screening, but laboratory confirmation remains essential when regulatory or commercial decisions depend on the answer.

Experience in the western United States illustrates the management burden. Pacific Northwest guidance has historically recommended action when any potato psyllid is detected because there is no dependable economic threshold for the disease risk. In areas of persistent pressure, growers have relied heavily on insecticide programmes aimed at the vector. That approach can suppress risk, but it carries cost, resistance and environmental consequences and may disrupt broader integrated pest management.

Breeding offers a longer route. Research in the United States has identified resistant or tolerant material in wild Solanum species and selected breeding clones, but promising germplasm is not the same as a commercially acceptable cultivar. Yield, maturity, processing quality, adaptation and market requirements still have to travel together. The fact that useful resistance exists is encouraging; the time needed to place it in growers’ hands remains the harder truth.

What PATAFEST is actually testing

PATAFEST is ambitious, but its coordinator, Christian Ghidelli of the Spanish technology centre FUNDITEC, has been commendably clear about what the project has and has not proved.

The consortium has characterised existing European, Ecuadorian and non-domesticated potato material and identified candidates carrying resistance genes. It has not created new varieties. It has developed a disease-risk model and moved biofertilisers, biopesticides and post-harvest treatments from the laboratory into a first year of field validation. Some formulations had to be changed for practical reasons; one powdered biofertiliser, for instance, is being reformulated as granules because application and logistics proved awkward.

That apparently mundane adjustment says something valuable. Innovation becomes real only when somebody can transport it, meter it, apply it with available equipment and justify its cost. A product that works in a controlled experiment but fails the day’s practical work is not yet a solution.

During the project’s current validation phase, camera-based sensors are being installed in industrial facilities in Spain and Germany. An early-detection application is also being prepared for industrial users and small farmers, particularly in Ecuador. Post-harvest research includes biological coatings, controlled atmospheres and volatile-organic-compound sensing intended to detect or limit dry rot, black dot and silver scurf as well as strengthen the wider disease-management system.

Ghidelli has also acknowledged the uncertainty. Biological responses vary, and several alternatives that performed well in the laboratory still have to demonstrate consistent value under field conditions. Regulatory approval and commercial affordability will present further tests. None of this work should be advertised as a finished replacement for conventional crop protection. The second season of validation is important precisely because the first one did not settle every question.

A smartphone is not an extension service

The proposed image-based application may become useful, especially if it helps a farmer or field technician recognise that a suspect plant needs closer attention. Yet Ecuador’s experience also warns against confusing a digital tool with a delivery system.

An app cannot compensate for unreliable connectivity, limited access to suitable devices, language differences or a shortage of trusted people who can interpret the result. It cannot, by itself, decide whether symptoms come from CLso, a phytoplasma, another pathogen, nutritional stress or a mixed infection. Most importantly, it does not stand beside a grower who must decide whether to spray, rogue plants, alter a rotation or risk the crop.

INIAP’s approach is more grounded. Researchers train technicians from Ecuador’s Ministry of Agriculture, who then work directly with growers. Communication materials have to be adapted for local languages and literacy levels and tested with the intended users. Farmer knowledge is also being brought back into the research: plants traditionally used as insect repellents are being evaluated rather than either accepted uncritically or dismissed as folklore.

That two-way exchange is not an attractive extra added to the science. It is part of whether the science works.

Preparedness without theatre

Europe is right to study a disease before it becomes established. That is not alarmism; it is what responsible biosecurity looks like. The most useful preparation is rarely dramatic. It consists of agreed diagnostic protocols, trained inspectors, traceable planting material, coordinated surveillance, reference samples, processor awareness and a clear chain of decisions for the first credible detection.

It also requires candour about trade-offs. Tighter phytosanitary controls can protect production while adding cost and delay to legitimate trade. Intensive vector control can reduce immediate disease risk while selecting for insecticide resistance and harming beneficial insects. Biological products may lower chemical dependence but can be variable, expensive or slow to register. Resistant varieties may eventually change the risk equation but will not automatically suit every market or climate.

Preparedness therefore cannot be reduced to one sensor, one resistant gene or one border rule. It is a system, and systems fail at their neglected connections.

The lesson that travels

The relevance of Ecuador’s experience extends far beyond the countries formally involved in PATAFEST. North American growers know the cost of managing an insect vector when processors have little tolerance for the defect it carries. New Zealand knows that strong island biosecurity does not make introduction impossible. European authorities know that the time to settle diagnostic and response arrangements is before a suspect sample appears. Potato regions in Africa and Asia, where seed systems and diagnostic capacity vary widely, have reason to watch all three experiences closely.

There is also a larger lesson for international potato research. Knowledge should not be imagined as flowing in one direction, from well-funded European laboratories to farmers elsewhere. In this project, Ecuador supplies the disease pressure, germplasm, field experience and hard-earned understanding that Europe presently lacks. Europe supplies finance, laboratories, engineering and a framework for coordinated testing. Each side holds something the other needs.

For me, that is the most credible form of international collaboration: not exporting a prepared answer, but admitting that the answer has to be assembled from different places and different kinds of expertise.

The potato industry often measures preparedness in equipment, chemistry and regulations. Ecuador’s experience suggests another measure: how quickly the least-connected grower receives advice that is accurate, usable and trusted. By the time a disease is obvious across a district, the expensive part of the lesson has already begun.

Europe still has the opportunity to learn before that point. The rest of us should do the same.