Fall armyworm causes $9.4 billion in annual crop losses across sub-Saharan Africa and South Asia a decade after the invasive pest arrived from the Americas

Summary

Spodoptera frugiperda, the fall armyworm, was first detected in West Africa in 2016, likely introduced through the international trade of agricultural commodities from its native range in the Americas. It spread across all 54 African countries by 2018, reached India and Bangladesh in 2018, and was confirmed in China by 2019. FAO estimates annual losses to maize and sorghum across sub-Saharan Africa at $9.4 billion, concentrated among smallholder subsistence farmers who lack affordable access to effective pesticides or biological controls. The African invasive population is a genetic hybrid of the two main US strains (maize-strain and rice-strain), which may account for its unusually broad host range of more than 350 plant species. Pesticide resistance has emerged in African populations, and no commercially available fully resistant maize variety exists.

The split

Agricultural development agencies led by FAO and CIMMYT have promoted integrated pest management (IPM) approaches combining biopesticides, biological control agents (particularly parasitoid wasps), early-warning monitoring through the FAMEWS mobile application, and tolerant maize varieties. African governments and smallholder representative organisations have argued that IPM approaches require technical capacity and sustained inputs that most subsistence farmers cannot access without subsidised extension services, and that the scale of investment in resistance breeding and biocontrol dissemination is insufficient relative to the $9.4 billion annual loss burden. Pesticide companies have expanded pyrethroid and organophosphate sales in Africa, but resistance emergence is already complicating this approach, and the cost of chemical control remains prohibitive for many smallholder farmers.

By the numbers

• 2016: year of first African fall armyworm detection (West Africa)
• 54: African countries with confirmed fall armyworm by 2018
• $9.4 billion: FAO estimate of annual maize and sorghum losses in sub-Saharan Africa
• 350+: plant species in fall armyworm host range
• 2018: year of South Asia arrival (India, Bangladesh, Sri Lanka)
• 2019: year of China confirmation
• 200,000+: African smallholder farmers trained by CIMMYT in IPM by 2024

Why it matters

The Fall Armyworm invasion of Africa and Asia is one of the most economically damaging biological invasions in recorded history. Maize is the most important staple crop across sub-Saharan Africa, and the fall armyworm's ability to destroy 10-30% of a maize crop has direct food security consequences for the approximately 400 million people in Africa who depend on maize as a primary calorie source. The pest is now permanently established across the tropics and subtropics outside the Americas, meaning eradication is not feasible; the only management option is suppression. The emergence of pesticide resistance within a decade of the invasion is a warning that chemical control will degrade as a management tool faster than biological control alternatives can be scaled.

What to watch

• Whether CIMMYT or other breeding programmes achieve full host-plant resistance in commercial maize varieties before pesticide resistance renders chemical control ineffective
• How China's fall armyworm management programme, which involves large-scale aerial pesticide application and emerging drone spraying, evolves
• Whether FAMEWS early warning monitoring achieves sufficient geographic coverage to enable timely coordinated responses at country and regional scale
• FAO's updated economic loss assessments for 2025 and 2026, and whether losses in Asia (India, Southeast Asia) are approaching the scale of African losses