When the American ‘Little Moth’ Lands in China’s Maize Fields
I knew he wasn’t being offensive, nor was he the sort to revel in others’ misfortunes. Beneath the offhand quip lay a sharper, more cynical reflection of the reality he understood.
A few years earlier, while managing a farm in Heyuan, Guangdong, he’d been told by the drone-spray operators about a particularly vicious pest in the maize fields. Eradicating it demanded heavy pesticide application, and notably, a section of that very field was dedicated to fresh sweetcorn.
Old Lei resolved then never to buy sweetcorn from outside again, though the pest itself never really registered in his mind—not even its name. It took two years before he returned to his hometown in Liuzhou, Guangxi, and crossed paths with the same creature once more, this time in his own family’s maize plot. Neighbours explained that it was precisely during his absence that the insect—officially known as the fall armyworm—had run rampant through their village.
“In my experience, you hardly ever used to need to spray maize. But now that we’ve got this pest, pesticide use has certainly gone up. For a single planting season, you’d need to spray at least six times, using roughly one sprayer tank per mu of land.” This direct confrontation truly drove home the severity of the fall armyworm threat. “The most infuriating thing about it is that it targets the maize heart leaves. That means you have to maintain a regular spraying schedule from the seedling stage onwards. Otherwise, the crop will be stripped by larvae within a week of emerging. Skip the sprays, and you’re looking at a total crop loss.”
II. Climate Change: The “Pesticide Treadmill” Accelerates
The fall armyworms that have invaded China primarily target maize. Last September, while conducting household surveys in Yanta Village, Kunming, Yunnan, we found that the mere mention of the fall armyworm instantly furrowed the villagers’ brows and hardened their gaze.
According to estimates from the aunties and uncles of Yanta Village, the fall armyworm could reduce maize yields by 10% to 15%, and in severe cases, cause total crop failure—a scenario closely matching what Lao Lei described. One auntie remarked: “We’ve had pests in the past, like aphids and springtails, but a single round of pesticide was enough to handle them. When the fall armyworm first appeared, ordinary sprays simply didn’t work, and we were at a loss.”
The real trouble lies precisely here. The intensive, pesticide-heavy agriculture of the Americas acted as a veritable breeding ground, allowing the fall armyworm to develop formidable resistance. This is one of the reasons they have been able to sweep across multiple continents in just a few years. The so-called ‘pesticide treadmill’ describes this vicious cycle born of over-reliance on chemical sprays: as insects develop resistance, farmers apply heavier doses until the pests become virtually immune, prompting the rush to develop new chemicals. The fall armyworm stands as a prime example. Because it now poses a severe threat to global food production, the UN Food and Agriculture Organization (FAO) has launched a worldwide coalition to combat the pest, yet it still cannot halt its relentless advance.
Yet just as humans find themselves stumped by the fall armyworm, climate change is hitting the accelerator on the ‘pesticide treadmill’.
Generally speaking, rising temperatures facilitate pest migration towards higher latitudes and altitudes. For every 1°C increase in temperature, crop losses for wheat, rice, and maize attributed to pests are projected to rise by 10–25%. The fall armyworm is no exception; it thrives in warmer conditions, with its development rate accelerating markedly as temperatures climb. Research predicts that under global warming trends, the species’ suitable habitat range in China will expand further. The high temperatures and low rainfall in Yunnan during 2019 were very likely key drivers behind the accelerated development, heightened reproductive capacity, and short-term population explosion of the fall armyworm.
III. “Skip the spray, and you’ll lose your shirt”
As with most farmers, Old Lei follows the same approach. Despite his extensive background in ecological farming and his familiarity with insect-repellent enzymes for pest management, he too finds himself forced to compromise in this instance.
“If conventional pesticides can’t shift those pests, insect-repellent enzymes certainly won’t do the trick.” On his own kitchen garden, Old Lei steadfastly refuses to use chemicals, yet the consequence is that fall armyworms burrow into his chillies and strip them bare; within a couple of days, the fruit rots and drops to the ground.
Consequently, while Old Lei avoids buying fresh corn from the market, he fully empathises with the large-scale maize grower in Guangdong: “Unless you’re just doing it for fun, when you’re cultivating over 100 *mu* of land with that kind of capital investment, who’s going to risk not spraying?”
Given that decades of pesticide overuse have already inflicted severe environmental and public health damage, China introduced a pesticide-reduction initiative in 2015. Consequently, the crux of managing the fall armyworm lies in a delicate balancing act: keeping pest populations in check and safeguarding crop yields without further escalating chemical usage.
Since the fall armyworm’s arrival in China, the state has channelled substantial dedicated funding and mobilised agricultural scientists across the country, integrating the pest into a surveillance and early-warning network spanning more than 3,000 agricultural counties in an effort to slow its northward advance. Each year, the Ministry of Agriculture and Rural Affairs publishes a technical framework for fall armyworm management. Core strategies encompass ecological management—harnessing farmland biodiversity through resistant cultivars, intercropping and relay cropping, and trap crops planted along field margins—alongside seed treatments, physical and chemical trapping, biological control, and the judicious application of agrochemicals. Several experts advocate prioritising physical and biological interventions, resorting to chemical sprays only as a last resort.
Across regions including Guangxi, Yunnan, and Henan, biological control techniques are being developed and scaled up to counter the pest’s growing resistance to synthetic chemicals. This involves the introduction of natural enemies such as parasitoid wasps, predatory bugs, and parasitic flies, alongside the development and field trials of biopesticides featuring *Metarhizium* species, *Beauveria bassiana*, and nucleopolyhedrovirus formulations.
The fall armyworm certainly instils a profound sense of urgency among farmers. This stems not only from its growing resistance to chemicals but also from its extraordinary capacity for reproduction and spread, often summed up by biologists as “flies far, feeds ravenously, and breeds prolifically.” As Old Lei puts it: “If you spot fall armyworm on a single maize plant today and leave it alone, within a couple of days every nearby plant will be infested. A few days later, that entire plot will be a write-off. So the moment you see them, you have to spray.”
Local farmers and residents in Yunnan have been equally plagued by this issue. When the fall armyworm first arrived in the province, they noticed that pests wiped out today would simply be replaced by newcomers flying in from neighbouring fields by tomorrow. Conditions only improved after the government organised professional teams to spray the entire affected region simultaneously. This approach is known as “unified prevention and control” – a campaign model where professionals apply pesticides uniformly across a targeted zone to combat outbreaks. Left to their own devices, smallholders can only “sweep their own doorsteps”. This forces them to spray more frequently, which only accelerates the development of pesticide resistance.
Yet, coordinated management is best suited to large-scale monoculture zones, meaning smallholders often miss out on this “benefit”. In Yunnan, agricultural expert Li Chunliang notes that unified spraying is particularly challenging for small-scale operations. When growing maize for animal feed, individual plots tend to be scattered, making uniform application impractical. For farmers growing fresh maize for human consumption, the challenge is even greater: because different growth stages require varying pesticide dosages, applying chemicals indiscriminately carries significant risks.
Given these constraints, Li Chunliang argues that the only viable path is to equip smallholders with scientific application techniques – such as selecting the right chemicals and rotating them strategically – so they can keep infestations in check without resorting to heavy chemical use.
Let’s be honest: farmers would rather not rely on such heavy chemical inputs. According to Old Lei’s calculations, pesticide costs have now climbed to around 200 yuan per mu, meaning that for many smallholders, growing maize often operates at a loss.
IV. More Than Just Pests Are Spreading
By the end of 2023, the Ministry of Agriculture and Rural Affairs had granted business licences to 26 companies for genetically modified maize and soybeans, followed by a new batch of biosafety certificates for genetically modified organisms in 2024. This marks the nationwide rollout of GM seeds across China, earning last year the title of the country’s “first year of GM commercialisation”. In line with this shift, the 2024 technical guidelines for fall armyworm management have been updated to prioritise “the adoption of insect-resistant GM maize”.
However, a fall armyworm management guideline published by the Food and Agriculture Organization of the United Nations (FAO) cautions that it is too early to draw firm conclusions on whether GM maize can effectively control the pest: “Bt maize has been shown to reduce fall armyworm damage, but the American fall armyworm has already developed resistance to certain Bt maize varieties.” (Note: Bt stands for Bacillus thuringiensis, a naturally occurring soil bacterium widely recognised as a beneficial biological insecticide. Scientists have transferred the insecticidal protein gene from Bt into maize, enabling the crop to produce the same protein. Following its approval for commercial cultivation in the United States in 1996, Bt maize has since been widely adopted across numerous countries.)
Yet, for a farmer like Lao Lei, a single maize crop now requires pesticide applications to jump from once to six times. Scientists race to develop new chemicals in a losing battle against the pests. In the end, we are left with no choice but to genetically modify the seeds themselves. Is this truly the adaptation we hope for?
The concern lies precisely here: not every technological effort to mitigate a crisis yields positive outcomes. Reviewing the past few decades of the fall armyworm’s escalating resistance seems to underscore a stark reality: humanity’s attempt to secure predictable yields by dominating nature has instead triggered ecological crises that thrust us into an increasingly uncertain world. We are left to ask: will the ‘pesticide treadmill’ keep running indefinitely? And how, exactly, will it finally grind to a halt?
References
https://d.wanfangdata.com.cn/periodical/rdzwxb201906028
http://www.ere.ac.cn/cn/article/pdf/preview/10.19741/j.issn.1673-4831.2019.0487.pdf
https://www.fao.org/fall-armyworm/monitoring-tools/faw-map/en/
http://journals.caass.org.cn/zgnxtb/CN/10.11924/j.issn.1000-6850.casb20191100857
http://www.moa.gov.cn/nybgb/2022/202212/202301/t20230104_6418252.htm
https://www.sciencedirect.com/science/article/pii/S2351989421005448
Editor: Ling Yu