Tar spot, a fungal disease in corn that could cost you up to 60 bushels per acre, is once again showing up across much of the Corn Belt and even as far south as Georgia.

Check out this latest map from the Crop Protection Network. The orange represents positive cases in 11 states, with Indiana having the widest outbreak.

Here’s what it looks like. The dots are fungal fruiting structures that severely interfere with photosynthesis. Brian and Darren Hefty, fourth-generation farmers, agronomists and hosts of Ag PhD, warned farmers about tar spot earlier this year at Commodity Classic. How should no-tillers treat it? Here’s what they recommend. 

Brian Hefty: “We like the really early timing of V4-V6 in the dry areas. But honestly, BASF has been talking about this ‘5 feet, time to treat’ thing (V8-V12), when we start talking about tar spot, that is maybe even on the early side. We’d tell you probably maybe a week or 2 before tassel. That'd be when I'd probably spray for tar spot and then spray again about 3 weeks later.”

Darren Hefty: “We’re seeing a lot of folks that are tank mixing, building their own 2-3 modes of action product. In some cases, you might be able to do it cheaper, but there are plenty of 3-ways that can be used.” 

The Hefty brothers compiled this table of corn fungicides for tar spot, comparing each brand name’s modes of action and approximate cost. Take a screen shot, you’ve got lots of choices. 

Watch the full version of this episode of Conservation Ag Update.