A harmful fungus called Southern rust is spreading throughout Indiana and is already impacting crops in 17 counties.
The infection affects corn and was first discovered in the southern United States before it traveled north to Indiana.
The spores, which look like orange rust spreading over the leaves of corn stalks, interfere with the photosynthetic abilities of the crop and could potentially reduce their overall yield.
Southern rust has been found in Indiana before, but it has arrived earlier in the season this year. Due to the current stage of development for most Indiana corn, as well as problems caused by an unusually wet summer, some are concerned the fungus may pose a greater threat this year.
Gail Ruhl is the senior plant disease diagnostician at the Purdue Plant and Pest Diagnostic Lab.
She says the first confirmed case of southern rust in Indiana this year was found in Parke County. It has since spread to other areas of the state, including Bartholomew County.
The fungus can be countered with fungicides, but Ruhl says the decision to apply the herbicides is made must be made on a case-by-case basis.
“Basically, farmers try to decide if a fungicide application is warranted by scouting the field very carefully and watching the weather to determine if and when a fungicide might be needed.”
In order for a case of southern rust to be confirmed, lab diagnosticians at the Purdue Plant and Pest Diagnostic lab conduct microscopic examinations of spore samples sent in by Indiana farmers.
Southern rust spreads faster during hot, humid weather, but slows down in cooler temperatures. Ruhl says it’s unlikely to affect corn in the vegetative stage.