Cotton Virus Circulated Undetected for Nearly 20 Years, Study Finds

A virus responsible for damaging cotton crops across the southern United States has been lurking in U.S. fields for nearly 20 years – undetected. According to new research, cotton leafroll dwarf virus (CLRDV), long believed to be a recent arrival, was infecting plants in cotton-growing states as early as 2006.

The findings, published in Plant Disease by USDA Agricultural Research Service researchers and cooperators at Cornell University, challenge long-standing assumptions about when and how the virus emerged in U.S. cotton. They also demonstrate how modern data-mining tools can uncover hidden threats in samples collected well before the virus was on anyone’s radar.

“CLRDV was officially detected in 2017, so the assumption was that it had only recently entered the U.S.,” said Alejandro Olmedo-Velarde, formerly a Cornell postdoctoral associate and now Assistant Professor in the Department of Plant Pathology, Entomology, and Microbiology at Iowa State. “Our study shows that this virus was actually present in the country’s Cotton Belt long before that. We found clear evidence of the virus in samples from 2006 in Mississippi, 2015 in Louisiana, and 2018 in California.”

To confirm the findings, the team conducted field surveys in 2023, collecting fresh cotton samples in Southern California. Lab testing confirmed that CLRDV is currently present in California marking the state’s first official report of the virus.