Deadly Fungal Disease Jumps Continents, Threatens Amazon Cassava Crops

A devastating fungal disease that has plagued Southeast Asian farmers for over a decade has made an alarming leap across the Pacific, now threatening cassava crops throughout the Amazon basin. Known as “witches’ broom disease,” the pathogen has transformed once-thriving fields into landscapes of yellowed, withered plants.

The crisis first emerged in 2023 when smallholder farmers in French Guiana discovered their cassava plants developing telltale symptoms: wilting leaves, withered stalks, and distinctive broom-like shoots sprouting from infected plants. Instead of harvesting the typical foot-long cassava roots that serve as a dietary staple, farmers found only stunted, unusable tubers. The fungal culprit, Ceratobasidium theobromae, attacks the plant’s vascular system, effectively choking off the nutrients needed for healthy growth.

Since its South American debut, the disease has rapidly spread across at least three Amazonian nations. From its initial foothold in French Guiana, it has likely reached Suriname and is now sweeping through Brazil’s northern states of Amapá and Pará, where entire cassava fields have been decimated. This expansion represents a worst-case scenario for plant scientists who had hoped to contain the pathogen to Asia.

The implications extend far beyond individual farms. Cassava, also known as manioc or yuca, is native to South America and serves as a crucial carbohydrate source for millions of people. The crop is also processed into tapioca flour, making it economically vital for rural communities. As international scientists race to develop containment strategies, the agricultural communities of the Amazon face an uncertain future for one of their most essential crops.