USA
October 25, 2021
With late July and early August rains increasing warm, moist air throughout the Midwest, noticeable breakouts of tar spot have infected the region’s cornfields. While many growers face challenges combatting the disease, NK® corn genetics have shown a strong resilience against it.
According to the Journal of Integrated Pest Management as featured in Entomology Today, tar spot was first detected in northern Illinois and central Indiana in 2015 and has steadily increased each year since, expanding to surrounding states. The rainy conditions of this summer, however, were favorable for the disease to spread more aggressively than in the past because it thrives in humidity, specifically in areas where leaves are consistently wet. The wind patterns of the season also have contributed to the outbreak, as the disease is spread by black spores that hatch and blow more spores into the air.
“I’d rank this year’s tar spot pressure a solid 8 or 9 out of ten in our area, and it came early enough to cause significant yield loss once the residual wore off,” said Wrangler Jones of Allied Cooperative. “I had a plot on an irrigation pivot and tar spot came in strong.”
It can take anywhere from 14 to 40 days after infection for symptoms to appear, with key visual indicators being browning leaves and raised black, circular fungal structures which appear as specks of tar splattered onto the leaf surface. Unlike other diseases that produce similar black specks, those resulting from tar spot do not rub off. These visual symptoms usually begin on lower leaves and rapidly move up the infected plant, appearing on both healthy and dead plant tissue. When the disease hits newer plants it shuts down their vital functions, ruining their ability to fill out corn ear kernels, ultimately reducing weight and yield. It also is more likely to result in faster plant death if contracted in early growth stages and has the potential to increase risk for other agronomic issues such as stalk lodging.
“While physiologically mature plants are much less likely to see the adverse effects of tar spot, developing plants are extremely at risk, and an infestation can mean great loss for growers who are not equipped with the right tools to combat the disease,” said Craig Mackey, NK agronomist. “Given the circumstances with tar spot this year, growers need to keep this in mind as they make their hybrid decisions going into next year’s planting season.”
The disease has proven to be a mystery to crop production with no known cure, making prevention key. Successful management and slowing of it has been found through hybrid selection, crop rotation and tillage as well as a preventive fungicide application such as Miravis® Neo fungicide. NK corn has numerous hybrids that have very good tar spot tolerance. NK0314, NK1026, NK1082, NK1188, NK1321, NK1523 and NK9175 are some of the best in the lineup, as they have shown impressive staygreen in the face of the disease, performing better in comparison to competitor brands and hybrids.
“Because there is no cure, genetic selection is the No. 1 priority for protecting corn against tar spot,” said Joe Bollman, NK corn product manager. “Our R&D team has had a strong focus on tar spot in our genetic selection process, and that is definitely showing in the field this year.”
Jones experienced first-hand the advantage NK hybrids offer against the disease. “We sprayed a fungicide and could see an immediate response,” said Jones. “Once it wore off, there was a night-and-day difference – the NK hybrid stayed green, compared to other hybrids, which indicates a higher response to fungicide or a better tolerance to tar spot.”
The same rigor used for the genetic selection for tar spot tolerance has been used in developing the Field Forged Series™. Launched for the 2022 growing season, this line-up of corn hybrids and soybean varieties combines proven performers and elite newcomers that offer maximized ROI potential for farmers.
“Genetic diversity in fields can give growers a way to handle various diseases and field conditions confidently,” said Doug Kirkbride, Syngenta Seeds corn product placement scientist. “Prioritizing such diversity has been part of the conversation for years at NK, making our hybrids some of the strongest options for disease protection.”
To learn more about NK, contact a local NK retailer or visit www.NKSeeds.com. Join the conversation online – connect with Syngenta at Syngenta-us.com/social and follow @NKSeeds on Facebook and Twitter.
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