Combating fall armyworms

Scientists make major breakthrough with local fungus strain DOREEN NAWA Lusaka

A TINY fungus grown in a Zambian laboratory could become one of the country’s most promising weapons against a pest that has spent nearly a decade ravaging maize fields. Scientists working for a not-for-profit intergovernmental organisation, CABI, have successfully harvested, for the first time, spores of a local strain of a naturally occurring fungus that infects and kills a fall armyworm called Metarhizium rileyi. The breakthrough, which follows three years of dedicated research and development, means the fungus has now been produced entirely in Zambia, ending years of reliance on spores produced at CABI’s laboratory in Egham, United Kingdom. For a country where maize is central to food security, the development could prove significant. The fall armyworm has become one of Zambia’s most damaging invasive agricultural pests, affecting at least 98 percent of smallholder farmers every cropping season and causing estimated annual losses of about US$159 million. The story of Zambia’s battle with fall armyworms – scientifically known as Spodoptera frugiperda and native to the Americas – began in 2016. The outbreak was first reported in December 2016, initially in Copperbelt Province, before infestations were reported in Eastern, Luapula, Lusaka and Central provinces. By January 2017, the pest had already affected more than 129,000 hectares of maize, turning what had started as scattered reports into a national agricultural emergency. Maize was not the only target as the fall armyworm is a highly polyphagous pest capable of feeding on a wide range of crops and grasses, including sorghum, millet, rice, wheat, barley, sugar cane and other plants. For Zambia, however, its attack on maize has been particularly damaging because maize is both a major staple food and an important source of income for smallholder farmers. Although the fall armyworm was new to Zambia in 2016, armyworms themselves were not – African farmers have battled armyworm outbreaks for decades. During severe outbreaks, vast numbers of caterpillars can appear almost simultaneously and move across fields in search of food, stripping vegetation as they go. But unlike some pests that attack only a narrow range of crops, fall armyworms can feed on more than 80 plant species. “This pest is deadly,” says Milaka Chasunkwa of Gota Gota Village in Chirundu. “I have been experiencing it for a decade now and treating it using pesticide is unattainable for me because of the high cost of medicines ideal for the management. “I tried the previous season to use pesticides thinking I have eradicated it forever, but surprisingly the next season it was back damaging more maize in my field. The maize is attacked from the leaves to the cobs, making it unredeemable.” The fall armyworm ability to spread rapidly, reproduce quickly and attack economically important crops make it particularly difficult to contain. Searching nature for an answer was the only way. The breakthrough began in 2018. Scientists from the Zambia Agricultural Research Institute (ZARI), the University of Zambia (UNZA) and CABI discovered Metarhizium rileyi occurring naturally in areas where fall armyworms were devastating maize. The fungus was already attacking the pest. That discovery changed the direction of the research. Instead of searching for a biological control agent somewhere else in the world, scientists could investigate an organism already found under Zambian conditions and naturally capable of killing fall armyworms. The discovery led to further research under the Village-based Biocontrol of Fall Armyworm in Zambia project, funded by the Australian Centre for International Agricultural Research (ACIAR), alongside CABI’s PlantwisePlus programme. Researchers began testing the fungus across Zambia’s three agroecological zones. They investigated both liquid and dry formulations, examining their effectiveness and determining the most appropriate timing and frequency of application. The goal was to develop a biological control option that could eventually form part of an integrated approach to fall armyworm management. For four years, however, the spores used in the research were produced at CABI’s laboratory in Egham, UK. They then had to be shipped to Zambia. That has now changed. For the first time, CABI’s laboratory in Zambia has successfully grown the local strain of M. rileyi on rice and harvested its spores entirely in-country. ZARI is already testing production using different varieties of rice, as well as sorghum, wheat and barley. Scientists want to identify which cereal provides the best conditions for producing the fungus efficiently and consistently. This work is crucial because discovering a fungus that kills fall armyworms is only the first step. The real challenge is producing enough of it, in the right formulation and at a cost that could make it practical for smallholder farmers. Scientists believe this local strain is well adapted to Zambian environmental conditions, giving it strong potential for use in augmentative biological control. Biological control could also help address some of the challenges associated with heavy reliance on conventional pesticides. CABI says nearly 43 percent of Zambian farmers use pesticides every season, while some farmers use highly hazardous products. Repeated or inappropriate pesticide use can create risks for farmers, consumers and the environment and can contribute to the development of pesticide resistance. The fungus offers a different approach — using a natural enemy to suppress a natural enemy. But researchers are cautious. CABI laboratory technician Sihle Nakombe has led the work on producing the spores. “Harvesting the first spores of M. rileyi is a great milestone for our research and skill development among young scientists,” Ms Nakombe says. “It is the result of three years of dedicated work to develop a biological control option for more sustainable fall armyworm management in Zambia, and we’re excited about where it can take us next.” Intern Sampa Kazembe, who also worked on the mass- production process, says the experience has provided practical laboratory skills and strengthened her understanding of biological control. “Working on the mass production of M. rileyi has been an inspiring chapter in my professional journey,” she says. “As an agronomy graduate, this experience has deepened my appreciation and passion for the role of biocontrol in building sustainable agricultural systems, while reinforcing my commitment to developing innovative, science- based solutions that protect both farmers and the environment.” Now the challenge is how to scale up and whether the laboratory success can eventually reach the farmer. CABI regional director for southern Africa Natasha Mwila says the successful production of spores from a locally sourced strain demonstrates the value of investing in local scientific capacity and developing biological solutions tailored to Zambia’s agricultural systems. “By harnessing naturally occurring organisms, we are advancing more sustainable approaches to managing fall armyworm while reducing reliance on conventional pesticides,” she says. PUBLISHED ON AUGUST 17, 2026 IN THE ZAMBIA DAILY MAIL