Denise Caldwell (she/her/hers)
Purdue University - Botany and Plant Pathology
West Lafayette, Indiana, United States
Raymond Garcia-Rodriguez
Plant Pathologist - Controlled Environment Assay Development
Bayer
Chesterfield, Missouri, United States
Richard Bittner
Controlled Environment Product Development: Disease and Pest Control Lead at Bayer Crop Science
Bayer
Chesterfield, Missouri, United States
Joseph Kaskowitz
Controlled Environment Product Development: Disease
Bayer
Chesterfield, Missouri, United States
Mikaela Breunig
Plant Pathologist at Bayer Crop Science
Bayer
Chesterfield, Missouri, United States
Mercedes Diaz-Arias
Technical Product Lead at Bayer Crop Science
Bayer
Chesterfield, Missouri, United States
Anjali Iyer-Pascuzzi
Professor
Purdue University
West Lafayette, Indiana, United States
Tar Spot is a yield-limiting disease of maize (Zea mays) in the US caused by the ascomycete Phyllachora maydis. Understanding the mechanisms of P. maydis colonization and evaluating control measures is critical for effective disease management. Growers use multiple commercially available fungicides to manage Tar Spot; however, the mechanisms and their efficacy at the microscopic level have yet to be examined. Thus, this set of studies aims to use histological and microscopic techniques to investigate the colonization process of P. maydis and assess the effectiveness of a commercially available, three-mode-of-action fungicide in susceptible and resistant maize hybrids. Three experiments were conducted. The first established a timeline for tissue collection in a susceptible maize genotype inoculated with P. maydis, with samples collected over 18 days. The second evaluated fungicide application timing to inhibit colonization and reproductive structure development in a susceptible hybrid. Lastly, we examined colonization differences between susceptible and tolerant hybrids to identify morphological traits linked to reduced fungal spread and reproduction. This research aims to bridge a crucial knowledge gap by offering cell-specific insights into the mechanism of fungicidal activity and host resistance to P. maydis. Our findings will help inform fungicide application protocols and hybrid selection strategies for maize growers, contributing to improved disease management that will mitigate the economic impact of Tar Spot while promoting sustainable agricultural practices.