Drought Staves off Tar Spot Presence in 2023

Tar spot has taken a new stronghold in U.S. corn fields in 2023. High humidity and more precipitation in certain areas make for prime tar spot conditions. However, drought has staved off some disease pressure compared to the 2021 outbreak. Farmers in roughly six states have reported tar spot so far this season.

University of Wisconsin’s Shawn Conley, a soybean extension specialist, says rainfall is good, but cropping systems need periods of wet and dry conditions to allow for intermittent leaf wetness. University studies show crops are most at risk when relative humidity exceeds 75%. A Purdue University report says the greatest damage can happen when leaf wetness lasts longer than 7 hours.

Read more on tar spot and corn disease data here.