Evaluation of Biorational Products for Managing Early Season Apple Scab and Cedar-Apple Rust in Iowa, 2024

Apple scab ( Venturia inaequalis) and cedar-apple rust ( Gymnosporangium juniperi-virginianae) are both major diseases of apples, causing defoliation and unmarketable fruit. This report evaluates the efficacy of biorational products for the management of primary apple scab and cedar-apple rust on leaves in the early part of the season. The trial was conducted in 2024 in Ames, IA, on four biorational products on 2-year-old Malus × domestica ‘Buckeye Gala’ and ‘Golden Delicious’ trees. All treatments reduced disease incidence under high pressure, with cultivar-specific differences in efficacy. Results support further integration of biorational strategies into early-season disease management programs in the Midwest.