A fungus that kills another fungus

Can a fungus kill another? And if so, how could that benefit us? This is the story of a discovery that transformed the world of fungicides used in agriculture to combat fungal diseases. It all began 55 years ago in the former Czechoslovakia…

In that country, two types of edible fungi—Oudemansiella mucida and Strobillurus tenacellus—were known to grow on decaying wood in forests. But until then, no one had noticed a curious detail: where these fungi thrived, no other fungi grew nearby.
 
It wasn’t until the 1970s that the reason became clear: these two fungi secreted a substance that killed any rival fungi daring to encroach on 'their territory,' potentially stealing moisture and nutrients. This natural fungicide, which harmed other fungi but not the ones producing it, was identified as betamethoxyacrylic acid. Scientists realized they had stumbled upon a promising breakthrough—here was a substance that could combat fungal attacks on agricultural crops. But it wouldn’t be that simple. The compound proved photochemically unstable and highly sensitive to temperature changes, making it impractical for commercial use.
 
Years later, in 1982, researchers at Zeneca Agrochemicals (now Syngenta) took this molecule apart and developed no fewer than 1,400 variants. Eventually, they created one that met the necessary conditions for effective agricultural use: azoxystrobin. Just seven years later—thanks to the compound’s excellent eco-toxicological profile—field trials began, demonstrating its ability to effectively fight fungal attacks across a wide range of crops without harming the plants or the environment.
 
Much like the natural fungicide secreted by those two fungi, azoxystrobin shared a similar mode of action, including a lack of resistance from target fungi. The molecule easily penetrated the cell walls of pathogenic fungi, reaching their mitochondria—the energy-producing organelles critical to fungal survival. By disrupting the electron transport chain, it halted ATP synthesis (the fungus’s vital energy source). Without energy, the fungus died, allowing the affected plant to resume normal growth.
 
Azoxystrobin revolutionized fungicides with unprecedented properties, becoming an essential ally in protecting crops worldwide. It offers preventive action (powerfully inhibiting spore germination and early fungal development) as well as curative and eradicative effects (remaining highly active against post-germination stages of various fungal species, whether applied before or after an infection).
 
Another standout feature is its exceptional toxicological and environmental profile. This was evident when it received its first registration in 1998 in Germany—a country known for its stringent Green movement standards. Just months later, the U.S. Environmental Protection Agency (EPA) granted its approval.
 
Rarely has an agrochemical company developed a product with such remarkable traits. This original, groundbreaking fungicide, with a mode of action unlike anything before it, proved effective against a broad spectrum of diseases—including downy mildew, powdery mildew, excoriosis, black rot, Alternaria, anthracnose, and Septoria—in over 60 commercially significant crops.
 
Today, azoxystrobin is no longer exclusive to one company; it’s marketed by numerous agrochemical firms under various trade names and concentrations, tailored to specific crops. But in its time, it was a true revolution that reshaped the world of agricultural fungicides.
 

A journey through the history of the pharmaceutical industry and one of its great laboratories that had its origins in Alfred Nobel...
“From Alfred Nobel to AstraZeneca” (Vicente Fisac, Amazon) is available in e-Book and print editions: https://a.co/d/9svRTuI