Hydrangeas thrive in the cool, misty uplands around Medellín, where small farms blanket the Andean hillsides in color. But across Colombia’s highland hydrangea regions, plants that once bloomed in dense clusters collapsed mid-season: leaves yellowing, stems wilting, roots turning soft and brown.

For smallholders, each loss threatened not only their fields but their contracts with buyers abroad. As one of Colombia’s most valuable ornamental exports, hydrangeas supply thousands of stems each week to markets in North America and Europe. In export agriculture, a single plant pathogen outbreak can ripple across global markets.

For years, growers sent samples to labs and were told the same thing: Fusarium.

“It looked like the obvious cause,” recalled Dr. Lilliana Hoyos-Carvajal, phytopathologist and profesora titular, facultad de ciencias agrarias, sede Medellín, Universidad Nacional de Colombia.

Quick to take action, Colombian farmers applied repeated fungicide soil drenches, replaced diseased plants, and rotated treatments, but the die-off continued to spread from bed to bed. Each lost plant was another painful blow for smallholders whose livelihoods depend on healthy hydrangeas.

But was Fusarium really the problem?

“They had tried everything and nothing was working,” said Dr. Hoyos-Carvajal. As a strong believer in epidemiological justice, she wanted to help.  

The farmers needed answers.

“We reanalyzed the case and concluded: it’s not Fusarium,” determined Dr. Hoyos-Carvajal. “There’s something we’re not seeing.” 

Protecting the hydrangea trade meant identifying the real culprit. But finding a single cause can be difficult in such a complicated growing environment.

The challenges of growing in Colombia

Colombia’s hydrangea belt winds up and down through steep Andean hillsides. Soils vary from volcanic to clay-heavy, and farms are often small, family-run operations spread across regions like Antioquia and Cundinamarca.

“We have the Andes and megadiversity, where many types of crops are grown together because all the microclimates exist here,” explained Dr. Hoyos-Carvajal.

Humidity, altitude and daily rain create ideal conditions for export-quality blooms, but also a great habitat for plant pathogens.

Each microclimate brings its own challenges, making it difficult to identify a single cause when disease strikes.

Turning to field diagnostics

Fusarium wasn’t the only possibility. Another soilborne pathogen thrives in wet, high-humidity soils: Phytophthora, an oomycete (water mold) known to cause root rot in ornamentals.

Phytophthora symptoms can closely resemble Fusarium, especially early on: both cause root and stem necrosis, leaf yellowing and plant wilt. The key differences are subtle and usually confirmed only through diagnostics.

“It’s a common pathogen,” said Dr. Hoyos-Carvajal. “But under certain circumstances, it doesn’t show up in the lab. Why? Because when you plate it, other microbes grow faster and take over the petri dish. So, you never see it.”

That’s why they turned to field diagnostics. “During a visit with Diane Plewa and Sneider Macha from the University of Illinois – doing the same kind of field visits we do with students – they brought Agdia test kits,” said Dr. Hoyos-Carvajal.

Together, Dr. Hoyos-Carvajal and Dr. Plewa began field testing with Agdia’s Phytophthora ImmunoStrips®. Because none of Agdia’s ImmunoStrips® require specialized equipment or electricity —just a small sample of symptomatic tissue and buffer solution — they could perform tests on site.

In a country where logistics and lab access can delay results by weeks, field diagnostics like Agdia’s ImmunoStrips® shorten that window, with tests showing results in less than 30 minutes.

According to Agdia’s validation report for this test, the assay detects more than 27 Phytophthora species with greater than 95 percent sensitivity and no cross-reaction with non-target genera.

Within minutes, clear results appeared on the test strip. “We got a positive diagnosis. That’s very important because it changes how we manage the disease,” said Dr. Hoyos-Carvajal.

“We started building a scientific framework to support growers: what’s okay, what’s not okay about this disease,” said Dr. Hoyos-Carvajal. The Universidad Nacional de Colombia worked in concert with Dr. Plewa and the University of Illinois. “We’re working on a solution, but now with a secure path: a well-done diagnostic test. . . We have positive results for a pathogen. So, we’re going to act – because the diagnosis gives us confidence.”

A change in strategy

With the right diagnosis, growers and researchers could finally focus their efforts on developing informed management strategies suited to local conditions.

As Dr. Hoyos-Carvajal explained, “Our first strategy is communication. Our work is built on trust. Trust with our growers. Trust with our students, who are like our partners.” Once farmers understand the disease, creative, environmentally responsible solutions can follow.

For Colombian hydrangea growers, the confirmation was empowering. After years of uncertainty, they finally understood the enemy they were fighting.

By combining rapid testing with local expertise, Colombian hydrangea growers now had a path forward to protect the quality of their blooms and the stability of Colombia’s export-driven agricultural communities.

The power of early detection

For smallholder farmers, access to simple, accurate field tools meant the difference between guessing and knowing.

By confirming Phytophthora on-site, farmers could make better irrigation decisions and protect healthy plants before infection spreads. 

It’s about giving farmers the tools to solve their problems. But this is not just about hydrangeas.

“The foundation is a solid diagnosis. Because it is the foundation for developing creative solutions in a biodiverse environment, where applying fungicides or chemical molecules can cause many collateral effects,” said Dr. Hoyos-Carvajal.

If farmers can diagnose and respond faster, they use fewer off-target chemicals and protect the environment.

It's better for everyone.

Want to bring faster diagnostics to your growers? Let’s talk.

Let’s equip your team with in-field tools that help farmers detect plant pathogens and protect their yield, their livelihood and their environment.

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