Skip to main content
APS Plant Health 2025 Main banner
Icon Legend
This session is not in your schedule.
This session is in your schedule. Click again to remove it.
ViewAttendees 8

TECHNICAL SESSION: Epidemiology

Comparative analysis of tar spot disease impact on corn health: disease pressure, fungicide efficacy and hybrid performance

Monday, August 4, 2025
2:15 PM - 2:30 PM HST
Location: Ballroom B/C
Abstract Text:

Tar spot of corn is a disease caused by the obligate ascomycete fungus Phyllachora maydis, which threatens corn production in the Americas by destroying the plant’s foliage, reducing yield and causing severe economic damage. In the United States, tar spot management relies on both the use of partially resistant varieties and chemical control. Although commercial fungicide products are labeled for tar spot control, our objective is to assess hybrid susceptibility under varying disease pressure and apply remote sensing to evaluate disease progression and yield loss. In 2024, field experiments in a randomized complete block design tested seven corn hybrids, fungicide application and three plant canopies at three locations in Michigan: Decatur, East Lansing and Mason. The non-treated plots showed a higher incidence and area under the disease progress curve (AUDPC) than the fungicide-treated plots (P < 0.001). East Lansing had developed the highest disease severity (10-20%), followed by Mason (1-9%) and Decatur (0-3%). Hybrid H3 consistently showed the highest AUDPC, while hybrids H7, H6, and H5 had the lowest values across locations and treatments. Yield differences were observed between cultivars but not among fungicide treatments with vegetation indices reflecting these differences. The results of this study provide a new perspective on evaluating tar spot under field conditions, highlighting the importance of inoculum pressure in tar spot development over time, fungicide efficacy and the impact on corn hybrid yield.