Deadly Fungal Disease Spreads to South American Cassava Crops

A devastating fungal disease that has plagued cassava crops across Southeast Asia for over a decade has now jumped continents, threatening food security in South America. In 2023, smallholder farmers in French Guiana first noticed their once-thriving cassava plants turning yellow, with leaves wilting and distinctive broom-like shoots sprouting from infected stems. When harvest time came, they discovered only stunted, useless roots where large, nutritious tubers should have been.

The culprit is “witches’ broom disease,” caused by the fungal pathogen Ceratobasidium theobromae, which attacks the plant’s vascular system. International scientists who investigated the outbreak in 2024 immediately recognized the telltale symptoms of this agricultural nightmare that has already caused widespread economic hardship across Asia. Despite hopes that the disease could be contained to its original region, it has now established a foothold in the Amazon.

The fungus has rapidly spread beyond French Guiana into at least three nations. It’s likely present in Suriname and is now sweeping through cassava-growing regions in northern Brazil, where entire fields in Amapá state have been decimated. The disease has also been detected in Pará state, raising fears about its continued expansion.

This development is particularly alarming because cassava—also known as manioc or yuca—is native to South America and serves as a crucial carbohydrate source for millions of people. The starchy root crop is essential for food security in many developing regions and is also processed into tapioca flour. The arrival of witches’ broom disease in the crop’s ancestral homeland represents a significant threat to both local communities and global food systems.