Tar spot has been found in 13 Indiana counties as of Thursday afternoon.
“We found it here in Indiana this year, I guess I turned on the map July 7th”, says Purdue field crop pathologist Darcy Telenko. She publishes the map on her website, indianafieldcroppathology.com.
“So, back in 2021, it was July 3rd. But if we look at the previous years, it wasn’t until the middle of July, end of July. So yes, now that we’ve kicked up early again it does have me a little concerned, but we’ve just got to watch what’s going on with the weather conditions.”
Telenko tells us on the latest Purdue Crop Chat podcast (found now at HoosierAgToday.com), that back in 2021, tar spot robbed some Indiana corn fields of up to 50% yield. Just because tar spot is showing up on Telenko’s map in your neck of the woods, she says that doesn’t mean get out there and spray right away.
“It means get out and scout. The map is telling you we found one or two lesions in the lower canopy in my go-to places for some of those samples where we’ve always found it annually… Those are the couple that we found early on. We’re getting more samples in this week where it’s shifting a little bit where we’re seeing a little more severity in those lower leaves. Now the crop is VT, tasseling silk. So, now we’re approaching the more optimum timing if we’re going to put fungicides out for any disease.”
Scouting now is more important than ever. Telenko says her research shows there is a “point of no return”, where a fungicide application won’t do much, if anything, for you.
“So, if you wait too long and the disease gets to 5% or more in that upper canopy, we’re probably not going to slow it down. A fungicide may or may not provide protection at that point. So, we need to be ahead of it for this one. But you need to scout and make an informed decision. Are you seeing diseases that you’re worried about in your fields? Have you selected hybrids that are more susceptible? Then make a decision to pull the trigger. Now, we can tell you the optimum timing, but I can’t tell you when you can get the airplanes or other things in the field.”
Telenko discusses tar spot and other corn and soybean diseases in the Purdue Crop Chat podcast, found below or wherever you listen to podcasts.
