Combatting an Invasive Pest Exacerbated by Climate Change

Fall armyworm has spread across more than 100 countries worldwide, setting unprecedented challenges for farmers. Recent climate events like hurricanes and extreme storm winds in 11 states is driving the typically southern predator northward in the U.S. The resilient pest has proved especially devastating in the developing world with the potential to destruct hectares of vital crops including maize, jeopardizing the livelihoods and food security of millions.

Last year, farmers in East Africa, Southwest Asia and areas of the Middle East battled their worst desert locust outbreak in decades. And as if that wasn’t enough, a second – and equally devastating —transboundary and invasive pest continues to invade parts of the eastern hemisphere: fall armyworm (FAW). Indigenous to the tropical and subtropical regions of the Americas, fall armyworm in maize (Spodoptera frugiperda) was first reported in 2016, followed by rapid spread throughout sub-Saharan Africa, and by 2018 began to spread like wildfire into the Indian subcontinent, China and Southeast Asia. In January 2020 it was detected in Australia in far north Queensland, and in a mere three months was considered established in the country. As of May 2020, it reached Mauritania, Timor-Leste and United Arab Emirates. During the first half of 2021, it was confirmed in New Caledonia and the Canary Islands of Spain in Europe. To date, fall armyworm has spread to over 70 countries. The outlook is dire: fall army worm comes with serious consequences.

A More Than 50% Potential Yield Loss Drastically Impacting Farmers’ Livelihoods

The insect is among the most destructive transboundary pests. The voracious invaders feed in large numbers on the leaves and stems of more than 350 plant species, including staple crops such as maize, cotton, rice, and sorghum, with maize being the preferred host. Maize is an important staple for more than 1.2 billion people in sub-Saharan Africa and Latin America, and it is the most important cereal crop in sub-Saharan Africa, accounting for over 30% of their people’s caloric intake. More than 300 million Africans depend on maize as their main food crop.

Fall armyworm’s hunger for maize not only causes significant losses to farmers, but also poses a serious threat to food security. The invaders are capable of crop destruction that can lower yields by more than 50%, drastically impacting farmer’s livelihoods. These losses hit smallholder maize farmers most directly, as the majority on average farm less than 1 hectare, relying on the crop to stave off hunger and poverty. Based on 2018 projections by The Food and Agriculture Organization of the United Nations (FAO), up to 17.7 million tonnes of maize are lost annually due to FAW alone  – representing enough to feed tens of millions of people and an average economic loss of $4.6 billion USD. In addition, recent research by the Chinese Academy of Agriculture (CAAS) suggests that the fall armyworm invasion has increased poverty and vulnerability among smallholders in China and Africa, with CABI estimating the costs to be as high as USD 9.4 billion annually.

The threat of the invasive fall armyworm is significant with the potential for establishment in other economically important crops due to its broad host range. In December 2019, the FAO launched a three-year Global Action for Fall Armyworm Control initiative, which aims to reduce yield losses caused by the pest and lower the risk of further spread by strengthening national capacities for sustainable management of FAW at a global level. Several activities have been promoted by FAO as follow-up including a “Prevention, preparedness, and response guideline”, farmer field schools (FFS) which have impacted over 15.000 people in over 30 countries, and an integrated pest management (IPM) demonstration package in eight countries: Burkina Faso, Cameroon, China, Egypt, India, Kenya, Malawi and the Philippines. Unfortunately, there’s no panacea. Despite multiple attempts, fall armyworm has never been successfully eradicated from any country it has invaded.  

Climate Change and Rising Temperatures Exacerbate the Challenge

Experts point to globalization, trade, transport routes and climate change as factors in the propagation of invasive insect pests. In the case of FAW, adult moths reproduce quickly and in large numbers with the ability to migrate for hundreds of miles on prevailing winds or large storm fronts — the most recent fall armyworm infestation in the Midwest U.S. come up with the hurricane winds causing damage to anything green in its path. In fact, according to a report captured with synoptic weather maps, one swarm migrated from Mississippi to Canada (about 995 miles or 1600 km) in 30 hours on a low-level jet stream – though this type of movement is highly unusual. Adult moths can travel 100 km (about 60 miles) per night, and female moths can fly more than 300 miles (about 482 km) before landing and laying their eggs – between 1,000 and 2,000 eggs in her life —laying them in masses of 150 – 200 eggs each. In warm climates, up to ten generations per year or more are possible.

In the case of maize, a female moth lays her eggs on the foliage of the plant and upon hatching just a few days later, the larvae begin to feed. FAW larvae can attack maize at all growth stages, but most often feed on the undersides of leaves, including young seedlings. Small holes known as windows are left behind as a result of their chewing and as the caterpillars near maturity, they can decimate an entire crop in a few days. And as rising temperatures increase rates of insect development and the number of pest generations, multiple generations can wreak havoc in suitable climates like Africa and Southeast Asia. For agriculture, this represents an opportunity to build more resilient agriculture, one that can face the second COP26 challenge: “Adapt to protect communities and natural habitats”.

More action needed to eliminate fall armyworm

So, what’s to be done? There are effective tactics farmers use to curb fall armyworm in North and South America where it has been for centuries – but early detection, universal knowledge and access to those technologies is a significant roadblock, especially for smallholder farmers. Thanks to the efforts of Global Action for Fall Armyworm Control, these tactics have made their way to Asia and Africa in recent years. Some of the more effective control strategies, however, have fallen susceptible to resistance, for example Bt resistance mutations have been detected in Puerto Rico or Brazil. It is a natural phenomenon for insect populations to develop resistance and happens when control strategies lack diversity. Experts broadly agree that diverse insect pest control strategies using many different tools and approaches that take location into consideration are needed.

Farmer education and community action are critical elements in the strategy to sustainably manage FAW. Key practices for curbing fall armyworm include the use of different agronomic practices such as push and pull, development of host plant resistance varieties including through biotechnology, effective pesticides, pheromone traps, or conservation and augmentation of natural enemies for biological control. Digital solutions such as mobile apps to collect and share real time vital data about infestation levels or machine learning and the use of algorithms along with sensors that could be used to automate the identification and capture of FAW by pheromone traps in the field, hold promise for sustainably managing fall armyworm. Access and training to deploy these new technologies is needed to combat the fall armyworm and protect those who are most vulnerable. In April 2021, the Food and Agriculture Organization of the United Nations hailed progress in the fight while stressing the need for continuing to drive awareness and scaling up engagement, concluding “There is still a lot of work ahead of us.”