Asian soybean rust left more than 20 soybean seed growers near Tampico, Mexico unexpectedly dealing with the disease. About 320 hectares, or 650 acres, were affected, resulting in defoliation and potential large yield losses.
Reports also indicate spore traps in Houston, Texas, captured Asian rust-like spores. Confirmation of rust in Texas makes the spread to the Midwest much more likely compared to infections in the Southeast.
ASR infections in Mexico began in January but became increasingly noticeable in March and April. Seed beans are generally harvested at the end of April into early May, so the majority of the affected acres should be out of the ground. Mexican growers will begin planting more soybeans closer to the Texas border in late May. According to Dr. Marty Wiglesworth, Syngenta technical brand manager, fungicides, the time gap between harvesting the seed beans and planting additional soybeans may be good news for U.S. soybean growers.
"We cannot foresee whether the impact on the U.S. crop will be minimal. We don't know at this point," Wiglesworth says. "It depends on whether there are nearby patches of volunteer soybeans or kudzu for ASR to live on until the newly planted Mexican crop becomes susceptible at R1. Scouting fields is the prudent thing to do."
Potentially, Wiglesworth says ASR could be equated to the wheat rust that comes yearly out of Mexico and Texas into the Midwest. "If ASR establishes itself on a regular basis in Mexico, one possibility is that it could follow a very similar pathway as wheat rust. Overwintering ASR present in Florida and Georgia has a harder time moving directly into the Midwest unless there are unusual weather patterns, but Mexico could serve as a more consistent source into the Midwest. At this time, however, experts believe the current risk for rust in east Texas is low."
There are currently no effective fungicides labeled for use in Mexico for Asian Soybean Rust control.