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Thursday, January 15, 2026

Locust swarms destroy crops. Scientists found a way to stop that

Arizona State University

A locust in the ASU Global Locust Initiative lab — image:
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.
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Credit: Quinton Kendall/ASU Knowledge Enterprises

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

As the director of Arizona State University’s Global Locust Initiative, Cease has a healthy admiration for these insects, even as she studies ways to manage locust swarms and prevent the destruction they cause.

Locust swarms, which may conjure images of biblical plagues and ancient famines, remain a serious problem worldwide. They can destroy crops across entire regions, ruin people’s livelihoods, and in some places, impact children’s education and future economic opportunities. Swarms can cover hundreds of square miles — equal to a major metropolitan area like New York City or Phoenix.

So, when Cease and her international team of scientists discovered a simple soil-based method to keep locusts from eating crops, they knew their work could change people’s lives. To the team’s knowledge, theirs is the first study to test this new method in real-world farming conditions and confirm that it works.

The researchers partnered with farmers in Senegal who experience outbreaks of the Senegalese grasshopper. This grasshopper does not form the extreme swarms like the desert locust, but its consistent outbreaks and smaller swarms can be more devastating for Senegalese farmers. These communities, which worked with Cease for previous studies, advocated for this larger study.

Each farmer grew two plots of millet — one treated with nitrogen fertilizer and one untreated.

Compared to the untreated plots, the treated plots showed three clear differences: fewer locusts, less crop damage and a doubled crop yield.

"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, also an associate professor with the ASU School of Sustainability and School of Life Sciences.

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

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

The Global Locust Initiative, part of the Julie Ann Wrigley Global Futures Laboratory, focuses on locusts and the systems that surround them. Environmental factors, biology and behavior, economic impacts, policies, and landscape management all feed into the cycle of locust destruction — and offer opportunities to break it.

Over 15 years of studying locusts, Cease found that plants growing in nutrient-poor soil promote locust outbreaks. These plants are high in carbs and low in protein.

“This carbohydrate bias, or the ‘donut diet,’ is optimal for populations of locusts and swarming grasshoppers,” Cease says. Just like runners who load up on carbs before a marathon, locusts need more carbs to fuel their migration.

In nitrogen-rich soil, plants are higher in protein and lower in carbs. These plants are bad for locusts to eat — their bodies can’t handle the extra protein and don’t get enough energy.

Protein-packed plants prevent pests

All this work led to the question: can we prevent locust damage by changing the protein-to-carb ratio of plants? Small lab studies and field surveys suggested the answer might be yes, but no one had tested it in open, working farmland. To Cease, that was the next logical step.

Two villages in Senegal that collaborated with Cease on previous studies advocated conducting the new study in their communities. Farms there suffer heavy crop damage from swarms of the Senegalese grasshopper.

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

The scientists were uncertain whether locusts might still enter treated plots via untreated areas, or whether the increase in plant protein would attract different pests.

The team assessed the number of locusts and damage to farmers’ plots three times throughout the growing season. They also recorded millet yields for each plot at harvest time.

The difference between the treated and untreated plots was significant. Treated plots had fewer locusts, less leaf damage to crops and a doubled millet yield at harvest. The team also found no evidence that nitrogen fertilizer made pest problems worse.

While the research team provided nitrogen fertilizer for the purpose of the study, it’s not practical for communities to use on a regular basis. To really work long-term, they need a way to add nitrogen to the soil that is affordable and good for the farmland.

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

The project’s funding, provided through USAID, was cancelled in early 2025. However, the farmers on the ground in Senegal are so encouraged by the results that they are continuing the compost system on their own.

“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 team is applying for additional funding to expand the project into other regions hard-hit by locusts.

Staying a step ahead of locusts

The U.S. has no locust species inside its borders. Why study them here at all? Cease says it won’t stay that way forever. She’s keeping her eye on the Central American locust, whose range reaches about 200 miles from our 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, we have enough reasons to study grasshoppers in the U.S. — 12 of them, in fact. They’re called the Dirty Dozen.

These 12 rangeland grasshoppers (plus one cricket) are top species of management concern in the western U.S., according to the U.S. Department of Agriculture. When they swarm, they can outcompete livestock for grass, creating a huge problem for ranchers.

The department relies on chemical pesticides to control the grasshoppers, but through the Global Locust Initiative, it’s identifying alternative treatments that are safer for human health and the environment.

The more we learn about locusts in other parts of the world, the better we can address migratory pests at home and prepare for the day when locusts make their way to the U.S.

DOI

10.1038/s41598-025-27884-z

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Soil amendments suppress migratory pests and enhance yields

Article Publication Date

15-Jan-2026

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

“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.

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.

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

Quinton Kendall/ASU Knowledge Enterprise

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

A Senegalese farmer and study participant inspects ripening millet in a field.

Credit

Marion Le Gall

Friday, December 12, 2025

Yuletide kissers, smooch without guilt: Research suggests your mistletoe didn’t harm its tree host

Oregon State University

CORVALLIS, Ore. – If mistletoe’s status as a nutrient-stealing freeloader has been cooling your holiday ardor, new research led by an Oregon State University scientist may help relight the fire.

A survey of urban forests in seven western Oregon cities found no observable connection between mistletoe infestation and negative health outcomes for the trees it was parasitizing.

So worry not: Your yuletide kissing tradition probably does not involve a tree killer. And as you’re setting concern aside, you might want to head outside.

“This is the best time of year to look for mistletoe because there are no leaves on the trees,” said College of Forestry professor emeritus Dave Shaw, an OSU Extension Service forest health specialist. “Also, chances are it will be found in an oak tree – most other trees don’t get infested. So if you are looking for a kiss, keep an eye out for oaks.”

Shaw and collaborators at OSU, the U.S. Forest Service and the Oregon Department of Forestry examined the occurrence of western oak mistletoe in city forests to learn about mistletoe hosts and gain insight into mistletoe management.

Common from Baja California to the northern Willamette Valley, western oak mistletoe is one of more than 1,400 species of mistletoe, a type of flowering plant that attaches to the branches of trees and shrubs around the globe.

Western oak mistletoe berries (on the female plants only, and toxic to humans) ripen in late fall or early winter and are eaten by western bluebirds and other birds, who disperse the seeds, most commonly on larger trees.

Mistletoe seeds are covered in a sticky substance that allows them to cling to branches. Mistletoes siphon food and water from their hosts via a bark-penetrating, root-like structure, sometimes to the detriment of the host tree.

“Western oak mistletoe is probably a benefit to wildlife in urban forests,” Shaw said. “On the other hand, there is the potential for negative impacts on amenity trees, which is why it’s important for urban forest managers to have assessments of mistletoe host range, both for future tree planting decisions and managing current tree populations.”

Western oak mistletoe occurs on native oaks and a collection of other hosts – including acacia, alder, aspen, birch, chestnut, locust, pear, poplar, walnut and willow – so vast that no definitive host list exists.

Shaw notes that urban forests often include a variety of non-native trees, planted historically for reasons that include aesthetics, adaptability, and rapid growth of shade-producing canopy. For this study, the researchers focused on introduced tree species in Salem, Corvallis, Eugene, Medford, Central Point, Rogue River and Ashland.

The scientists conducted their surveys by driving, walking and biking city streets, parks, university campuses and arboreta, with the goal of visually examining all non-native tree crowns for the presence of mistletoe plants.

“Urban forests are unique settings that allow for a wide assortment of potential hosts to be exposed to mistletoe seed,” Shaw said. “We observed western oak mistletoe in 227 non-native trees, of which 85% were pin oak or northern red oak.”

Among the rest, 12% were other oak species, meaning just 3% were not some kind of oak tree – even though non-oaks were in the majority.

Western oak mistletoe infested trees of all size classes, but only six of the 227 infested trees were less than 10 centimeters in diameter and just nine were less than 10 meters tall. Only one infested tree looked to be in poor condition, 14 were in moderate condition, and 212 appeared to be in good condition.

“That suggests mistletoe, at the levels of infestation we saw, is not adversely impacting tree health,” Shaw said. “Of the 42 trees with greater than 20 mistletoe plants in their crowns, none was in poor condition, one was moderate and 41 were in apparently good condition.”

Mistletoe has been a symbol of health, love, vitality and fertility in multiple cultures since ancient times, and the tradition of kissing under mistletoe has its roots in 18th century England.

“The word ‘parasite’ can carry negative connotations, but mistletoe is a remarkable and beautiful plant with centuries of cultural importance behind it,” Shaw said. “It was nice that our survey showed that it wasn’t causing appreciable harm to its hosts.”

OSU professor emeritus Max Bennett also participated in the study, which was published in Northwest Science. The other collaborators were retired Forest Service researcher Don Goheen, retired Oregon Department of Forestry scientist Alan Kanaskie, and current ODF scientist Scott Altenhoff.

Journal

Northwest Science