Can parasitic weeds be tricked into dying? Scientists think so

For centuries, farmers have struggled to keep their crops safe. Droughts, pests, and poor soil are common challenges. But among the most silent and destructive enemies are parasitic weeds.

These plants do not grow on their own. Instead, they cling to healthy crops and steal vital nutrients. In regions already battling food insecurity, the damage can be catastrophic.

Now, researchers at the University of California, Riverside may have found a unique solution. Their work focuses on a curious plant hormone and a clever trick: make the weeds destroy themselves. This breakthrough opens a new chapter in how we think about weeds, crops, and survival.

Parasitic weeds cause major crop losses

In sub-Saharan Africa and parts of Asia, fields of rice, sorghum, and other staples often fall victim to parasitic weeds. These aren’t just nuisances. They can wipe out entire harvests. For farmers depending on a single crop to feed their families and communities, the loss is devastating.

Unlike typical weeds, these invaders don’t grow alongside crops. They embed themselves into the host’s root system. Once attached, they steal water and nutrients directly. Crops weaken before they can fully develop. The result is lower yields, hunger, and economic hardship.

Farmers in these regions often lack access to strong herbicides or expensive biotechnology. That leaves them with limited tools to stop the spread. This is where UCR’s research offers new hope – by using the weeds’ own instincts against them.

How parasitic weeds sense plant signals

At the heart of this discovery lies a class of plant hormones called strigolactones. These chemicals, though not widely known outside of plant science, are extremely powerful.

Inside the plant, the hormones help regulate growth, root development, and responses to stress. But their external role is even more fascinating.

“Most of the time, plant hormones do not radiate externally – they aren’t exuded. But these do,” said UCR plant biologist and study co-author David Nelson. “Plants use strigolactones to attract fungi in the soil that have a beneficial relationship with plant roots.”

This natural relationship between fungi and plants benefits both sides. The fungi help gather nutrients from the soil, while the plant offers carbohydrates. It’s an elegant system – until parasitic weeds enter the picture.

The weeds have evolved to recognize strigolactones. To them, the hormone is a green light. When they detect it, they germinate and prepare to attack. That’s where the researchers saw their opportunity.

Tricking parasitic weeds

What if the weeds could be triggered to germinate when no host is present? Without a host, the weeds would sprout, fail to attach to anything, and die. This is the approach UCR’s scientists are testing.

“These weeds are waiting for a signal to wake up. We can give them that signal at the wrong time – when there’s no food for them – so they sprout and die,” Nelson said. “It’s like flipping their own switch against them, essentially encouraging them to commit suicide.”

This concept isn’t just theoretical. One parasitic plant, broomrape, produces thousands of seeds on a single stalk. Those seeds lie dormant in the soil for years. But once they detect strigolactones, they awaken.

By releasing synthetic versions of the hormone at the wrong time, researchers aim to reduce their numbers before they can cause damage.

Building synthetic hormones in the lab

To control this process, scientists need a way to produce strigolactones outside the plant. That’s where microbial engineering comes in. Led by Yanran Li, formerly at UCR and now at UC San Diego, the team created a novel system using bacteria and yeast.

The researchers engineered E. coli and yeast cells to mimic the chemical pathways found in plants. These microbes became tiny hormone factories. With them, the team could study each step of strigolactone production in a clean, controlled setting.

“This is a powerful system for investigating plant enzymes,” Nelson said. “It enables us to characterize genes that have never been studied before and manipulate them to see how they affect the type of strigolactones being made.”

Beyond research, this method may allow large-scale production of synthetic strigolactones. That could mean practical, affordable tools for farmers in the future.

Evolution, enzymes, and possibilities

The team’s work also sheds light on how these hormones evolved. They identified a key metabolic branch point — an internal decision made by the plant to direct its chemicals either inward or outward. This may explain how strigolactones took on their unique role outside the plant body.

Understanding this evolution opens more doors. It helps scientists design more precise synthetic versions. They can fine-tune the signals to work in different environments or target specific weeds.

Researchers are continuing to test the strategy in more realistic settings. The idea sounds promising, but real fields are unpredictable. Soil types, weather, and local plant life all affect the outcome.

“We’re testing whether we can fine-tune the chemical signal to be even more effective,” Nelson said. “If we can, this could be a game-changer for farmers battling these weeds.”

Parasitic weeds reveal wider hormone uses

Though the research began with crop protection in mind, strigolactones may offer broader benefits. Studies suggest they might have anti-cancer or anti-viral properties.

There is also interest in using them to fight citrus greening disease, which has devastated Florida’s citrus industry.

Because they affect how cells grow and communicate, these hormones are catching the attention of scientists in medicine and environmental science. What started as a way to help plants may one day help people, too.

Clever solution to a growing problem

Parasitic weeds are a quiet threat to global food supplies. But this new approach offers a clever counterattack. By understanding and manipulating natural plant signals, researchers may have found a way to protect crops without harming the environment.

This work is still developing, but its promise is clear. With careful research, dedicated teams, and innovative tools, science may help turn one of nature’s sneakiest tricks into an advantage for farmers everywhere.

The study was made possible in part by the NSF-funded Plants3D traineeship program at UCR. Led by Professor Julia Bailey-Serres, the program brings together biology, engineering, and creativity. Its goal is to prepare students for a future where food insecurity grows alongside climate change.

The study is published in the journal Science.

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