"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 was published in Scientific Reports. 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 was canceled 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.
Source - https://phys.org
