A single application is enough to cure the tree permanently
In the chestnut groves of northeastern Portugal, where families have drawn their livelihoods from the land for generations, science has quietly answered one of agriculture's most stubborn prayers. Since 2015, researchers at the Polytechnic Institute of Bragança have deployed a biological treatment against chestnut cancer — a fungal disease that once left farmers with little more than the choice between slow loss and chemical compromise. With a 95% success rate across more than 200,000 trees, the work now enters a new phase, as the institute and Portugal's agricultural authority commit to five more years of research and the long road toward bringing the cure to every farmer who needs it.
- Chestnut cancer, caused by the fungus Cryphonectria parasítica, has long threatened the livelihoods of thousands of small farming families in Bragança and Vinhais — Portugal's heartland of chestnut production — with roughly one in ten trees in the region infected.
- A biological fungicide developed at IPB has achieved 95% efficacy, permanently curing trees with a single application by redirecting the tree's own energy away from fighting the pathogen and toward regenerating healthy tissue.
- More than 200,000 trees belonging to over 3,000 producers have already been treated, but access remains limited to farmers enrolled in the research program, leaving the broader region's orchards still vulnerable.
- A new five-year agreement between IPB and Portugal's agricultural authority extends the program while simultaneously building the scientific record required for commercial homologation — the regulatory approval that would open the treatment to all farmers.
- IPB's president is confident approval could arrive within the five-year window, a milestone that would transform a decade-long laboratory success into a freely available tool capable of reshaping an entire agricultural sector.
In the chestnut orchards of northeastern Portugal, a quiet revolution has been unfolding since 2015. The Polytechnic Institute of Bragança developed a biological treatment against chestnut cancer — caused by the fungus Cryphonectria parasítica — that has now cured more than 200,000 trees with a 95% success rate. This week, the institute and Portugal's agricultural authority formalized an agreement to extend the program for another five years.
The disease has long been one of the gravest threats to the Bragança and Vinhais districts, home to Portugal's largest concentration of chestnut growers. About one in ten trees in the region carries the infection, and for decades farmers faced a grim set of options: chemical pesticides, gradual decline, or outright loss. The biological treatment changed that entirely.
Researcher Eugénia Gouveia explained that the product works by essentially persuading the tree to stop recognizing the fungus as a threat, freeing it to redirect energy toward growing new, healthy tissue. Unlike chemical alternatives, a single application cures the tree permanently without harming human health or the environment — an elegance that sets it apart.
More than 3,000 producers — mostly family farms and small agricultural businesses — have participated over the past decade. Yet the treatment remains confined to research enrollees, meaning its full potential across the region is still unrealized.
The critical next step is commercial homologation, the regulatory approval required before the product can be sold and used freely. Paula Cruz Garcia of Portugal's agricultural authority noted that the ongoing program serves a dual purpose: actively helping farmers while gathering the scientific data needed to secure that approval. IPB president Orlando Rodrigues expressed confidence the process could be completed within the five-year extension, at which point the treatment would move from experimental program to open market — and from a laboratory achievement to a tool that reshapes Portuguese agriculture.
In the northeastern corner of Portugal, where chestnut orchards have sustained farming families for generations, a quiet revolution has been unfolding since 2015. A biological treatment developed at the Polytechnic Institute of Bragança has cured more than 200,000 chestnut trees infected with a fungal disease that once seemed unstoppable. The treatment works with a 95% success rate, and this week the institute and Portugal's agricultural authority signed an agreement to extend the research program for another five years.
The disease in question is chestnut cancer, caused by a fungus called Cryphonectria parasítica. It is one of the most serious threats to chestnut production in the Bragança and Vinhais districts, which together account for the country's largest concentration of chestnut growers. About one in ten trees in the region carries the infection. For decades, farmers had limited options: watch their trees decline, apply chemical pesticides repeatedly, or accept the loss. The biological treatment changed that calculation entirely.
Eugénia Gouveia, the researcher leading the program, explained how the treatment works. The biological product targets the fungus itself, essentially teaching the tree's immune system to stop recognizing the pathogen as a threat. Once the tree stops fighting the fungus as an invader, it redirects its energy toward growing new, healthy tissue. The elegance of the approach lies in its specificity: it does not harm human health or the environment, and unlike chemical treatments, a single application is enough to cure the tree permanently. "It is a highly effective system, highly specific, and it does not interfere with human health or the environment," Gouveia said.
The scale of the impact is substantial. More than 3,000 producers have participated in the program over the past decade. These are not large industrial operations but family farms and small agricultural businesses for whom chestnut production represents a significant part of their livelihood. The treatment has been applied only to trees belonging to farmers enrolled in the research program, which means the full potential of the cure has not yet been realized across the entire region.
The next hurdle is commercial approval. The product does not yet exist on the market; it requires homologation—the formal regulatory sign-off that allows a treatment to be sold and used broadly. Paula Cruz Garcia, deputy director-general of Portugal's agricultural authority, emphasized that the current work serves a dual purpose: it is actively helping farmers control the disease while simultaneously gathering the scientific data needed to eventually win that approval. "What matters to all of us, both to the agricultural authority and to the institute, is supporting farmers in controlling this scourge that affects our chestnut trees," she said.
Orlando Rodrigues, president of the Polytechnic Institute, expressed confidence that homologation could come within the five-year extension period. Because the treatment is biological rather than chemical, the regulatory pathway may be simpler than it would be for a synthetic pesticide. The institute is already preparing the documentation needed to submit for commercial approval. Once the product reaches the market, it will no longer be confined to research participants; any farmer facing chestnut cancer will be able to access it. That shift from experimental program to commercial product represents the moment when a laboratory success becomes a tool that reshapes an entire agricultural sector.
Notable Quotes
It is a highly effective system, highly specific, and it does not interfere with human health or the environment— Eugénia Gouveia, researcher leading the program
What matters to all of us is supporting farmers in controlling this scourge that affects our chestnut trees— Paula Cruz Garcia, deputy director-general of Portugal's agricultural authority
The Hearth Conversation Another angle on the story
Why did it take a decade to treat 200,000 trees if the method works so well?
The program was always research-based, not a commercial operation. The trees treated were part of a controlled study involving willing farmers. The institute needed to gather data on efficacy, safety, and long-term outcomes before asking regulators to approve it for general sale.
What happens to the farmers right now, before homologation?
They continue to participate in the program. The treatment is still being applied to their trees at no cost to them, as part of the research agreement. But they cannot buy it themselves, and their neighbors cannot access it yet.
Is there a reason this particular fungus was so hard to fight before?
Chemical pesticides work, but they require repeated applications and they kill indiscriminately. This biological approach is different—it works with the tree's own immune system rather than against the fungus directly. That specificity is what makes it elegant, but it also took years to develop and test.
What changes when the product is homologated?
Everything becomes commercial. Farmers can buy it. Distributors can stock it. The institute can license it. The treatment moves from a research footnote to standard agricultural practice across the region and potentially beyond.
Is there any risk in waiting five more years?
The disease does not stop. Every year, more trees become infected. But the institute believes the data they are gathering now will actually speed up the approval process when they apply. Rushing to market without solid evidence could backfire.