Tar spot gains attention of USDA-ARS

Tom J. BechmanEARLY STAGES: Agronomists say growers need to learn to identify tar spot at this stage. This specimen was growing in Bayer’s fungicide demonstration plots at the Farm Progress Show.Hi-Tech Farming: The newest corn disease in the U.S. is targeted by researchers.

Tom J Bechman | Nov 18, 2021

Tar spot was first detected in the U.S. in 2015, but it now has the undivided attention of a USDA Agricultural Research Service research team based in West Lafayette, Ind. Growers fight this corn disease with fungicides. However, Steve Goodwin, an ARS plant pathologist, says plants that have resistance to tar spot are preferable.

While participating universities conduct research on timing of fungicides and other control measures, Goodwin and his team are concentrating on four fronts:

1. Screening current material. The team is screening existing commercial varieties and germplasm lines for resistance or susceptibility to tar spot. The goal is to help growers adjust management practices as soon as possible depending upon which hybrids they grow.

2. Developing molecular markers. These tools will identify Qrtsc8, the gene that confers tar spot resistance. Investigators are also exploring why some plants that lack this gene are still resistant, since an unknown gene or genes could be involved.

3. Determining biocontrol potential. A microbiome of organisms was found on tar spot-resistant plants, but not on susceptible plants. Researchers want to know how these organisms, plant growth stage and the environment are interconnected in the progression of tar spot.

4. Understanding how tar spot works. Scientists also want to learn how the tar spot fungus uses several proteins to short-circuit defenses of susceptible plants. Identification of these proteins could lead to better detection of different strains of the fungus and its severity in the field.