Corn School: Assessing tar spot impact for 2023


Tar spot leaf disease has been a little tardy in 2023, but the later-arriving yield robber is still having an impact on the Ontario corn crop.

Ontario Ministry of Agriculture, Food and Rural Affairs plant pathologist Albert Tenuta says a dry start to the growing year meant tar spot arrived a little late in 2023 but wet summer growing conditions enabled the disease to catch up and establish in mid-July before really taking off in late August.

On this episode of the RealAgriculture Corn School, we visit with Tenuta at one of his tar spot research locations near Rodney, Ont., where he tests hybrid tolerance to the disease, fungicide timing and efficacy, and evaluates new management tools that may help better control the disease in future crop years.

For 2023, Tenuta says field location and disease history, hybrid selection, and local weather conditions will influence how the disease impacts the crop. As combines roll though fields across the province, he expects growers who have tar spot in fields will see a 10- to 30-bushel per acre yield impact. That’s similar to 2022 but significantly less than 2021 when the yield hit ranged from 30 to 60 bushels. (Story continues after the video.)

In his research plots, Tenuta is testing more than 100 hybrids to assess their tolerance to the disease. When it comes to fungicides, he tests a range of products and timings, including application at the V10, VT/R1 and R3 timings.

In the video Tenuta also takes a look at promising experimental fungicides, as well as new genetics from the International Maize and Wheat Improvement Center (CIMMYT) in Mexico that could give growers better defence against the disease in future growing seasons.

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