b'FIGHTINGSOUTH AMERICA ISknown for its fields of soybeans, but for the past few decades those fields have been threatened by one deadly diseaseBACK Asian Soybean Rust (ASR). While farmers have fought back with resistant soybean varieties and management strategies, the disease has always come roaring back. AGAINSTThere is hope on the horizon though with new soybean varieties on the way.Asian Soybean Rust is in fact the biggest disease issue affecting tropical ASIANsoybean production, particularly in SouthDiana Horvath, president of 2BladesAmerica where soybean used to be grown year-round. With no break in the growing season, the pathogen really built up, Diana Horvath, president of 2Blades, explains.SOYBEANThe ASR pathogen is found in bothcausing significant levels of defoliation North and South America, but the hotunder the right environmental conditions. weather of the southern hemisphereTan to reddish brown lesions grow as the continent makes it a huger threat todisease advances. Plants will prematurely RUST farmers there. According to Loren Giesler,lose their leaves as it progresses.an extension plant pathologist with theWith the right conditions, as soon as University of Nebraska-Lincoln, ASR isthe spores of the fungus get into the soy-caused by Phakopsora pachyrhizi whichbean field, the crop is destroyed in as little is an aggressive pathogen. It can causeas three weeks, Horvath says.With new Asian Soybean Rustyield losses ranging from 10 - 80%.For South American nations, theyre resistant soybean varieties onIts most common symptoms can bethe perfect hosts for ASR. The patho-the way, theres hope for Southfound on the leaves starting in the lowergen thrives in tropical hot conditions, canopy, Giesler writes. Lesions can alsoshe adds. The pathogen is a bio tropical American farmers. Ashley Robinson develop on petioles, pods, and stems.fungus that can live on a wide range of Once the plant starts flowering develop- host plants, not just soybeans. ment of ASR symptoms happens fastIn South American nations, such as A soybean field in Brazil infected with Asian Soybean Rust.PHOTO: SERGIO BROMMONSCHENKEL60/ SEEDWORLD.COMOCTOBER 2023'