In Brazil, rainy weather provides ideal conditions for soybean rust, a dangerous fungus that threatens one of the country's most important crops. Growers are on high alert for the emergence of rust spores, which thrive in wet conditions and can spread quickly from farm to farm through the air, traveling up to several kilometers along a destructive path.
Brazil is the world's leading exporter of soybean. In the early 2000s, rust began infecting soybean farms there for the first time. The damage was catastrophic for yields: rust-infected plants developed brownish-red spots, and their leaves withered and fell away if left untreated. Until now, growers confronting this devastating fungus reacted by making more and more applications of fungicides, which were losing efficacy due to resistance. Spraying more often was costly and inefficient as it required more product, more labor and increased fuel costs.