Locust swarms may meet their match in protein-enriched crops
Swarms of locusts devouring a farmer’s livelihood may seem apocalyptic, but major locust infestations are a regular problem in farming communities around the world. These locust swarms – dense, buzzing packs of certain grasshopper species – can cover hundreds of square kilometers, and the insects consume large amounts of vegetation and threaten global agriculture. In the western United States, a hotspot for grasshopper and cricket outbreaks, pastures essential for livestock grazing suffer annual losses estimated at $1.2 billion.
In a study recently published in the journal Scientific reportsscientists from Gaston Berger University in Senegal, the Global Locust Initiative at Arizona State University (ASU), and real farmers facing repeated infestations of Senegalese grasshoppers (Oedaleus senegalensis), identified a surprisingly simple strategy. Enriching the soil with nitrogen, the main building block of proteins, could help fight pests through their diet.
Hacking the Locust Diet
In parts of the Horn of Africa, the Arabian Peninsula and southwest Asia, locusts have hit farmers in numbers not seen in decades. In response, communities treated farmland with chemical insecticides and biopesticides. Fighting the 2019 to 2021 locust invasion in this region cost around $300 million. Scientists are also studying locust swarms from Central America to Mexico that could spread to the borders of the United States, where locust swarms have largely disappeared since the early 1900s. And as climate change creates warmer and wetter conditions, some researchers warn that some species of locusts could expand their ranges.
In Senegal, the potential new solution lies in how the Senegalese grasshopper fuels its swarming behavior. Protein is at the bottom of the locust food pyramid and incorporating it could help stem swarming. In field trials, crop plots treated with nitrogen-based fertilizers produced crops high in protein and low in carbohydrates. This is a much less palatable meal for the species, as it relies on a high-carbohydrate diet to create fat stores that fuel population growth and long-distance migration.
For several months, in central Senegal, the ASU and Gaston Berger team worked with 100 farmers from two village areas. Each farmer grew a grain called millet on two plots: one plot treated with commercial nitrogen fertilizer and one untreated plot. The scientists then surveyed the field three times during the growing season for pest abundance and damage. They found that the fertilizer treatment significantly reduced pest abundance and crop damage, while increasing millet yield.
The researchers are among the first to demonstrate this type of outbreak management strategy with the Senegalese grasshopper, which is just one type of grasshopper with tendencies to invade locusts. Although all locusts are grasshoppers, not all grasshoppers are locusts – and only a handful of thousands of grasshopper species are considered true locusts.
Arianne Cease, director of the ASU Global Initiative, shares Popular science that she hopes this research will help farmers around the world manage infestations of grasshoppers and locusts originating in agricultural fields, using soil-based strategies.
“Locust outbreaks are a very complex and far-reaching global challenge,” says Cease. “When these upsurges occur, they significantly affect people’s livelihoods. It is important for us to recognize how dangerous locust infestations can be to food security and economic security. And we must have a diverse set of strategies to manage them sustainably.”
A scalable solution?
According to biologists, locusts thrive under specific, often complex environmental conditions, such as above-average rainfall that creates moist soil ideal for breeding, as well as periods of drought that lead to resource scarcity and force density. Close spaces and suitable breeding conditions among locusts can activate sudden and rapid breeding and collective behavior, leading to epidemics.
Daniel Gebregiorgis, a climatologist in the Department of Geosciences at Georgia State University, says that while the nitrogen fertilizer-based method of locust control is a promising solution, scaling presents a possible challenge because outbreaks often occur in remote areas. Many locust control strategies also face obstacles when applied at scale in places with limited connectivity.
Gebregiorgis points out that this new research is particularly important as human-caused climate change is leading to an increase in locust outbreaks. In particular, it claims that an increase in cyclone activity that brought heavy rains to the main desert breeding areas of the Arabian Peninsula and East Africa fueled massive locust invasions in the region in 2020.
“Due to global warming, many regions are receiving above-average rainfall and, coupled with increasing soil temperature and humidity, there are increasing conditions for locusts to breed,” says Gebregiorgis. Popular science. “Along with increasing cyclone activity as well, this fundamental change in climate is the most important trigger for locusts. I would call locust outbreaks one of the clearest manifestations of the climate crisis today.”
According to Cease, human behaviors such as overgrazing and overfarming can also create conditions conducive to swarming. Overgrazing by livestock and intensive cropping can degrade land and cause soil erosion, creating nitrogen-poor soil that gives rise to carbohydrate-rich plants that support locust growth and help sustain swarms traveling long distances.
“Just insects doing their job”
As their next steps, researchers at Gaston Berger University in Senegal, led by locust biologist Mamor Touré, are using compost fertilizers, rather than more expensive commercial fertilizers, to achieve the same effects in a more accessible and sustainable way. Cease says their work with Senegalese researchers supports farmers as active participants in locust management. It can also combat the perception that locust swarms are random, even malignant, forces of nature or even divine will.
“There’s this narrative, largely inspired by our religious stories, that locusts are a scourge and they come when you do bad things,” Cease says. “But, really, these are just insects doing their job – and many aspects of how we manage our landscapes or how we broadly influence climate impact the likelihood of these locusts forming swarms.”
The best new PopSci 2025 releases
