Non-chemical ways to fight pestsAn unceasing stream of biotic and abiotic stresses threaten food security and health.
Over the past few years, Nepal’s agriculture sector has been hit by several biotic and abiotic stresses including new crop pests and pathogens. Among them feature migratory pests, which periodically make their appearance in the country, as well as invasive ones. The latter comprise organisms that are entirely new to Nepal, often originating far off parts of the world, and invade new territories through inter-country trade of agricultural goods and commodities, international travel or tourism. Climate change can also facilitate the arrival of new species, for example, by shifting their long-distance movement patterns or by making crops more susceptible to pest attack.
Though the National Plant Quarantine Office is tasked with keeping Nepal free of invasive pests, it is critically understaffed and under-equipped. A lack of well-trained personnel, outdated laboratory facilities and anaemic funding levels has let Nepali government officials fight an unequal battle with these crop-consuming critters. There are 15 quarantine check posts in Nepal, including one at Tribhuvan International Airport in Kathmandu. Though they frequently intercept unwelcome crop pests or diseases, they are unable to stem the tide of new invasions. Every year, new pests either make it across the long land borders with neighbouring China and India or hitchhike from distant locations in people’s suitcases or commercial shipments.
One of the most prominent pests is the fall armyworm (Spodoptera frugiperda), a night-flying moth originally from the Americas where it annually affects maize, rice and sugarcane production in the United States, Brazil and Mexico. Its larvae are especially voracious and cause extensive leaf-feeding within the maize whorl or lead to spoiling of the maize cobs. In 2016, the fall armyworm made its unwelcome arrival in western Africa. By 2018, it had been recorded in India’s Karnataka state, as if it had put on its proverbial seven-league boots to cross the Arabian Sea. It wasn’t long before the pest showed up in Nepal and neighbouring Bangladesh, China and Bhutan.
Eradication of this pest is entirely unfeasible and pest-induced losses will likely be felt for decades. In Nepal, maize is grown on less than 1 million hectares, and its cultivation constitutes a central feature of the daily lives of hundreds of thousands of Nepali farmers.
The fall armyworm will surely impact farmers’ livelihoods in Nepal and across Asia in a negative way. For example, in southern China, maize farmers have largely reverted to synthetic pesticides to tackle fall armyworm outbreaks. Since 2019, local pesticide application frequencies have increased three-fold. The repeated application of those toxic chemicals isn’t only costly, especially for resource-poor smallholder farmers, but also carries clear risks for farmer health and the environment.
Recent work by Wageningen University has unveiled how 97 percent of Nepali vegetables contain pesticide residues—often at levels that pose clear risks for human health. Pesticide contamination is most exacerbated in tomato, eggplant, and chilli—crops in which native and invasive pests have free rein. Like the fall armyworm, the tomato pinworm (Tuta absoluta) has antipodal origins, and made its first appearance in Nepal in 2016. It has since proliferated across the country’s farmlands.
Other pests such as the potato tuber moth (Phtorimaea opercullela) were first spotted in the 1960s and are causing ever more serious problems–likely aided by global warming. Climate change possibly may also be at play in orienting locust swarms towards Nepal. Throughout history, outbreaks of the desert locust (Schistocerca gregaria), or salaha in the Nepali language, have frequently been recorded in neighbouring India. However, it wasn’t until 1962 that Nepal also experienced an invasion by these devastating crop pests. Last year, swarms of millions of desert locusts once again covered the Nepali skies. As with the fall armyworm or the invasive tomato pests, Nepali farmers once again embraced synthetic pesticides to tackle these six-footed foes.
By looking for quick fixes and easy solutions, we tend to forget that chemical toxins are not the only available tools in the farmers’ plant protection arsenal. Pest damage can be minimised by diversifying cropping systems, incorporating organic matter in the soil, using disease-free planting material or adopting proper crop spacing. This way, a lot of trouble can be avoided. Also, on a healthy farm, there are hundreds of beneficial organisms that consume pests and thus prevent crop losses. Ants, earwigs, ground beetles and social wasps abound in Nepal’s farmlands, and all have fall armyworm caterpillars for breakfast.
Farmer Field School
Back in 1997, the Food and Agriculture Organisation (FAO) of the United Nations launched its Farmer Field School programme in Nepal. With generous funding from Norway and different UN agencies, the Farmer Field School programme trained tens of thousands of farmers through a novel learning-by-doing approach. Wide-eyed and with a sense of wonder, farmers discovered the various beneficial organisms that live on their farms, observed how they preyed upon key crop pests, and came to value the related ecological processes.
As a result, Nepali farmers gained confidence in non-chemical crop protection tactics, and they were able to lower their pesticide use by 70 percent without any yield loss, thus reaping net income gains of 20-40 percent. Now, nearly 25 years later, it isn’t only recommended to bolster Nepal’s quarantine services but to also breathe new life into these Farmer Field School training modules. No doubt, its observation-based learning approaches will optimally equip Nepal’s farmers to tackle the unceasing stream of new crop pests, and thereby defuse imminent food security threats. Also, Nepali farmers don’t find themselves alone in their battle with crop pests; our six-footed opponents are best addressed hand-in-hand with other Asian countries and international collaborators.