Tar spot is still new to the Midwestern corn fields and is quickly becoming a problematic disease. Agronomists are advising farmers to act now to protect their corn yield potential, since cases have already been confirmed in fields across the Corn Belt.
Golden Harvest agronomy manager for the East, Steve Wilkens says this year?s outbreak is becoming a little different from past years.
?We have found tar spot not necessarily a lot earlier than what we’ve seen in years past. But, in some areas of the Midwest, planting was delayed, and therefore the crop is younger in its maturity from when we’ve picked up on tar spot in years past. There’s a longer duration of this plant’s life that we’re going to have to protect from tar spot. This year?s a little bit different as we’ve seen larger outbreaks in more east-central/south-central Iowa, central Wisconsin, so it’s going to be a problem regardless of where the majority of the corn acres are in the central, the eastern, and even the southern Corn Belt. We’ve seen it pick up here in a little bit different geography from where we’ve had it in years past.?
Wilkens says tar spot has a 21-day latent period, so it?s time to get out and scout fields for signs of this disease now.
?Know the conditions, and if the conditions are right for tar spot, now that we’re getting into many areas, the VT timing of application, we just urge people to spray your fields. Understand there are apps out there – Tar Spotter is one of them from U.W. Madison – because the conditions are really what needs to be driving our decisions. I’m not going to say it’s too late, because it’s not, but there’s a lot more coming from an infection that’s taken place here that our naked eye can’t see. Now’s the time to spray for many of us heading into pollination, but even after that, understand your genetics. Are they susceptible? Do they have a level of tolerance? Your territory. Do you have it in the area? Have they had it in the past? Do I have the right conditions for it? And then make the decision whether or not to spray.?
Wilkens mentions the physical characteristics that growers need to look for when scouting fields for tar spot potential.
?The lower canopy is the first place you want to look for it. Then if you start to find these black specks, take your thumb and make sure you can’t rub it off. If you can, it’s some sort of a cosmetic deal. If you can’t, that’s a good indication of tar spot. You’ll also see a little bit of a raised bump and a little bit of yellow material around the black spot, and that’s a telltale sign it’s truly tar spot. It’s not something else. And if there’s ever any question, grab a leaf sample, send it to a lab, and they can go ahead and diagnose it for you, but that’s a really good sign that you got tar spot in the field.?
Wilkens gives advice about what farmers can apply now to prevent tar spot from hurting their corn crop potential.
?We want to key in and encourage growers to make that VT fungicide application, but I think we need to be contemplating even more than that in the back of our mind, like a good quality three-way mix fungicide that has good activity on tar spot. We probably have about a month of really good activity. If conditions remain favorable throughout the growing season do think it’s very necessary for growers to contemplate what a second application could mean during the grain fill.?
For more tar spot management recommendations, farmers can contact their local Golden Harvest Seed Advisor or agronomist.
