A virus damaging cotton crops has been present in American fields since at least 2006, far earlier than previously thought. New research reveals that cotton leafroll dwarf virus, officially detected in 2017, spread undetected across key growing regions. The findings underscore the value of reanalyzing old data to uncover hidden agricultural threats.
Scientists have discovered that cotton leafroll dwarf virus (CLRDV), which harms cotton plants in the southern United States, was infecting fields as early as 2006. Previously assumed to be a recent arrival after its official detection in 2017, the virus quietly spread through major cotton-growing states for nearly two decades.
The study, published in the journal Plant Disease, involved researchers from the USDA Agricultural Research Service and Cornell University. By reexamining archived genetic samples and public databases, the team identified CLRDV in material from Mississippi in 2006, Louisiana in 2015, and California in 2018. To confirm current presence, they conducted field surveys in Southern California in 2023, marking the state's first official detection.
"CLRDV was officially detected in 2017, so the assumption was that it had only recently entered the U.S.," said Alejandro Olmedo-Velarde, now an assistant professor at Iowa State University. "Our study shows that this virus was actually present in the country's Cotton Belt long before that."
The research also uncovered traces of the virus in a cow's digestive tract from a California study, likely from contaminated plant-based feed. This suggests broader dissemination before identification, though animals do not appear to be infected.
The findings may link CLRDV to bronze wilt, a debated cause of long-standing crop damage. "Now, as more studies align with our findings, the idea is gaining traction," Olmedo-Velarde noted. "It could help explain long-standing crop losses and inform virus monitoring strategies moving forward."
Dr. Michelle Heck of the Agricultural Research Service stressed the implications for farmers: "For growers, the findings offer both a caution and a call to action. CLRDV has been in U.S. fields far longer than anyone realized, and it may be more widespread than current reports suggest."
Overall, the work highlights bioinformatics' role in revealing overlooked plant diseases through existing data.
