Evaluation of fungicides to control geranium rust, 2025

Geranium rust, caused by the fungal pathogen Puccinia pelargonii-zonalis, is a destructive disease of geranium in greenhouse production. On leaves, geranium rust typically develops as small chlorotic spots on the upper leaf surface with raised, rust pustules on the underside of the leaf. Eventually, leaves become necrotic and may abscise. This report evaluates the efficacy of spray programs with conventional fungicides for the management of geranium rust. The trial was conducted in 2025 in Storrs, CT on greenhouse-grown geranium ‘Americana Salmon’. Results from this trial will help in developing management programs for this disease.