Evaluation of Humic Acid and Chitosan Additives for Corn Disease Management in West Lafayette, Indiana in 2025

Corn diseases such as tar spot ( Phyllachora maydis ), gray leaf spot ( Cercospora zeae-maydis ), northern corn leaf blight ( Exserohilum turcicum ), Curvularia leaf spot ( Curvularia lunata ), southern rust ( Puccinia polysora ), and Physoderma brown spot ( Physoderma maydis ) are frequently found in Indiana corn. Whereas, tar spot, gray leaf spot, northern corn leaf blight, and southern rust are the main foliar diseases that can cause significant yield loss. This report evaluates the efficacy of humic acid and chitosan additives in corn ( Zea mays ‘P0035AM’) compared to a standard fungicide product. The trial was conducted in 2025 in West Lafayette, Indiana. Disease incidence and severity, canopy greenness, lodging, harvest moisture, test weight, and yield were collected for each treatment. Low disease pressure was observed in Central Indiana. Treatments with Impact SIX chitosan (1.0 pt) and Monty’s Liquid Carbon (1.0 qt), both alone and combined with generic azoxystrobin + propiconazole (10.5 fl oz), applied at VT/R1 or Monty’s Liquid Carbon at V5, led to significantly lower lodging percentages than the nontreated control. Monty’s Liquid Carbon applied at R1 alone or in combination with generic azoxystrobin + propiconazole (10.5 fl oz) reduced the incidence of Physoderma brown spot. The findings will provide corn producers with valuable guidance for implementing humic acid, chitosan additives, and fungicide treatments and determining the most effective application timing for disease management.