Scientists Found a Way to Make Crops Unappetizing to Locusts

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Healthier soil can stop locusts before they start eating. In Senegal, nitrogen-rich crops kept locust numbers down and doubled harvests, offering a sustainable alternative to pesticides. Credit: Shutterstock

By changing what crops eat, scientists found a way to make locusts lose their appetite—and save harvests.

“They’re very destructive when there’s a lot of them, but one-on-one, what’s not to love?” says Arianne Cease. She is talking about locusts.

Cease directs Arizona State University’s Global Locust Initiative, where she studies how these insects behave and how to reduce the damage they cause. While her work focuses on controlling locust swarms, she also holds a deep respect for the species she studies.

Sydney Millerwise Holds Migratory Locust — Arizona State University PhD student Sydney Millerwise holds a migratory locust in ASU’s Global Locust Initiative lab. A new study by an ASU team and international collaborators identifies a strategy to manage locust populations and prevent damage to crops. Credit: Quinton Kendall/ASU Knowledge Enterprises

A Global Threat That Still Hits Hard

Locust swarms often bring to mind stories of biblical disasters, but they remain a very real threat today. Around the world, swarms can wipe out crops across vast areas, destroy livelihoods, and in some regions disrupt education and long-term economic stability. A single swarm can stretch across hundreds of square miles — equal to a major metropolitan area like New York City or Phoenix.

That is why Cease and her international research team paid close attention when they uncovered a surprisingly simple way to discourage locusts from eating crops. To their knowledge, this was the first time the approach had been tested in active farmland and shown to work outside controlled settings.

Gregarious Locusts — “All locusts are grasshoppers, but not all grasshoppers are locusts,” says Cease, an associate professor with the ASU School of Sustainability in the College of Global Futures. A locust in a “solitarious” phase is shy. It acts like a regular grasshopper: avoiding others of its kind, appearing a camouflage green and staying in one area. A locust in a “gregarious” phase is just the opposite — it gathers with other locusts, wears bright colors to stand out and migrates huge distances in search of food. Here, gregarious locusts gather inside their enclosure in the Global Locust Initiative lab at Arizona State University. Credit: Quinton Kendall/ASU Knowledge Enterprise

Testing a Soil-Based Solution in Senegal

To evaluate the method, researchers partnered with farmers in Senegal who regularly deal with outbreaks of the Senegalese grasshopper. While this species does not form massive swarms like the desert locust, its frequent appearances and smaller groupings can be especially damaging for local farmers. These same communities had worked with Cease before and pushed for a larger, more ambitious field study.

Each participating farmer planted two millet plots — one treated with nitrogen fertilizer and one untreated.

The results were striking. Compared to untreated fields, fertilized plots had fewer locusts, noticeably less damage to leaves, and millet yields that were twice as high.

Arianne Cease and Mamour Touré — Arianne Cease (left) served as the principal investigator of this USAID-supported project, and Associate Professor Mamour Touré (right) of Université Gaston Berger in Saint-Louis, Senegal, was the lead author of the study. Credit: Arianne Cease/Global Locust Initiative

“This breakthrough represents an important step forward in the sustainable management of migratory pests, offering a community-based tool that expands the available treatment options,” says Cease, who is also an associate professor in ASU’s School of Sustainability and School of Life Sciences.

The study was published today (January 15) in the journal Springer Nature. Associate Professor Mamour Touré of Université Gaston Berger in Saint-Louis, Senegal, served as the lead author, while Cease was the principal investigator for the USAID-supported project.

“The results are of major importance to the scientific community and also to Senegalese farmers,” Touré says. “The study gave them a better understanding of grasshoppers and locusts, as well as a practical way to control them at the local level.”

Docile Solitarious Locust — Like a werewolf exposed to moonlight, a locust is a grasshopper with the potential to completely transform under the right conditions. Out of approximately 6,800 described species of short-horned grasshoppers, only 19 are considered locusts. Over 15 years of studying locusts, Associate Professor Arianne Cease with the ASU School of Sustainability, discovered that plants growing in nutrient-poor soil promote locust outbreaks. These plants are high in carbs and low in protein. A key goal of her research is to improve sustainable ecosystem management and rural livelihoods. Credit: Quinton Kendall/ASU Knowledge Enterprise

Why Soil Quality Shapes Locust Behavior

The Global Locust Initiative, part of the Julie Ann Wrigley Global Futures Laboratory, examines locusts within the broader systems that influence outbreaks. Climate conditions, insect biology, land management, economics, and policy all interact to drive cycles of destruction — and offer possible points of intervention.

Over more than 15 years of research, Cease observed a clear pattern. Crops grown in nutrient-poor soil tend to encourage locust outbreaks. These plants are rich in carbohydrates and low in protein.

“This carbohydrate bias, or the ‘donut diet,’ is optimal for populations of locusts and swarming grasshoppers,” Cease says. Much like endurance athletes who load up on carbs, locusts depend on carbohydrate-heavy food to fuel long-distance movement.

Plants grown in nitrogen-rich soil tell a different story. They contain more protein and fewer carbohydrates, making them a poor food source for locusts. The insects struggle to process the extra protein and do not get enough energy to sustain themselves.

Senegalese Farmer Plowing Millet Field — An ASU and international research team partnered with 100 farmers from two villages in Senegal for the study. Farmers grew two plots of millet — one treated with nitrogen fertilizer and one untreated. Here, a Senegalese farmer works in the field during the experiment. Credit: Arianna Cease

Protein-Packed Plants Prevent Pests

This insight led to a key question. Could adjusting the balance of protein and carbohydrates in crops reduce locust damage? Previous lab experiments and field observations hinted at the possibility, but no one had tested the idea on working farms. For Cease, testing it in real agricultural conditions was the logical next step.

Two Senegalese villages that had collaborated with her before volunteered to host the study. Their farms regularly suffer severe losses from Senegalese grasshopper swarms.

In the experiment, 100 farmers each grew two millet plots—one treated with nitrogen fertilizer and one left untreated for comparison.

Researchers initially worried that locusts might move into treated plots from nearby untreated fields, or that higher protein levels could attract other pests. To track outcomes, the team counted locusts and measured crop damage three times during the growing season, then recorded yields at harvest.

The findings were clear. Fertilized plots had fewer locusts, less leaf damage, and double the millet yield. The researchers also found no signs that nitrogen fertilizer increased other pest problems.

Senegalese Farmer — A Senegalese farmer and study participant inspects ripening millet in a field. Credit: Marion Le Gall

From Fertilizer to Compost

Although nitrogen fertilizer was supplied for the study, it is not a realistic long-term solution for many communities. Sustainable control depends on affordable methods that also protect soil health.

“Ongoing work is focused exclusively on compost, and we seem to be getting the same results,” Cease says.

USAID funding for the project ended in early 2025, but the farmers involved have continued using compost on their own. Encouraged by the outcomes, they have adopted new practices without outside support.

“Farmers unanimously stated that they no longer burn crop residues after land clearing, but instead practice composting to fertilize their fields, thereby helping to reduce grasshopper infestations. This technique was fully mastered thanks to the project,” Touré says.

The research team is now seeking new funding to expand the approach to other regions heavily affected by locusts.

Senegalese Farmer Shows Improved Soil — A participating Senegalese farmer shows his field with improved soil from composting. Composting is also the focus of ongoing research by the science team. Credit: Arianne Cease

Preparing for Future Locust Threats

The United States currently has no native locust species, but Cease says that could change. She is closely watching the Central American locust, whose range comes within about 200 miles of the U.S. border.

“We can say with pretty high certainty that Texas will be very suitable for locusts in about 10 to 15 years,” Cease says. “Whether or not they will create a problem is yet to be determined, but it’s something that we should definitely be aware of.”

Even without locusts, grasshoppers already pose major challenges in the U.S. There are 12 species known as the Dirty Dozen.

According to the U.S. Department of Agriculture, these 12 rangeland grasshoppers (plus one cricket) are among the most concerning pest species in the western United States. Large outbreaks can strip grazing land and compete directly with livestock, threatening ranchers’ livelihoods.

While chemical pesticides remain the primary control method, the Global Locust Initiative is working to identify safer alternatives for people and the environment.

Insights gained from locust research overseas may prove essential at home, helping the U.S. prepare for future invasions and manage migratory pests more sustainably.

Reference: “Soil amendments suppress migratory pests and enhance yields” 15 January 2025, Nature.
DOI: 10.1038/s41598-025-27884-z

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