Farmers in three counties in Kansas have reported a disease that affects corn called tar spot. The fungal disease has spread from Mexico to several midwestern states including Kansas, particularly in Doniphan, Brown and Jefferson counties. Tar spot spreads through spores that are carried by the wind and farm equipment. The disease first appeared in the U.S. in Indiana and Illinois in 2015. The fungus infects corn leaves and creates back spots called stroma. Within the stroma, the fungus produces spores that continue to infect throughout the growing season. It attacks leaf tissue and can rapidly cause the plant to die. The disease can reduce yields by 20 to 100 bushels per acre by reducing ear size and kernel fill.
Rodrigo Onofre, a professor at the Department of Plant Pathology at Kansas State University, says “it has the potential to be really destructive and farmers need to be aware.” He says there are ways to manage it. Farmers can keep an eye out for tar spot, report any sightings to the local extension agent, and manage the disease using fungicides. It can be difficult to detect, but, one way is to use a wet cloth and try to clean the leaf, if it comes off, it’s not tar spot.
