Tar spot threatens Indiana corn crops

By Andi Anderson

For over a century, tar spot fungal disease in corn avoided the U.S. “Tar spot had not been detected in the U.S. prior to 2015, but it has been endemic in several Latin American countries, starting in Mexico in 1904,” said C.D. Cruz, associate professor at Purdue University. In 2015, it appeared in two of Indiana’s counties and by 2022, it spread to 16 states and Ontario, Canada.

The fungus also impacts crops in 15 other countries across Central and South America, the Caribbean, and U.S. territories like Puerto Rico and the Virgin Islands, Cruz reported in Plant Disease.

Researchers are investigating the origins, pathways, and variations of the pathogen. “Maybe we don’t have those populations here yet, and they could potentially be much more damaging than the ones currently present,” Cruz noted.

Cruz's team uses a blend of statistics, data science, epidemiology, microbiology, AI, and computer vision to study tar spot. Their work is supported by USDA grants totaling nearly $1.1 million.

High-tech data collection and analysis aim to provide rapid and accurate information for stakeholders. “There are opportunities in integrating AI-based digital technologies and point-of-care diagnostics,” Cruz said.

Collaborators include experts from Colombia, Mexico, Ecuador, South Korea, and the U.S. The team has developed digital methods for quantifying tar spot and other diseases using AI and computer vision. For example, the SCDA algorithm successfully quantified tar spot trends under field conditions.

Purdue’s Mohammad Jahanshahi, an expert in civil and electrical engineering, collaborates with Cruz. Together, they adapted AI techniques used for civil infrastructure to agricultural disease monitoring.

Their efforts include integrating drone imagery with weather data to model tar spot epidemics, enhancing problem-solving through interdisciplinary expertise.

In 2015, tar spots affected two of Indiana's ninety-two counties. Only a small number had survived by 2022. By then, the Pest Information Platform for Extension and Education reported that the fungus had spread to 16 states and Ontario, Canada.

Photo Credit:usda