Efficacy of Flutriafol Soil Injections for Controlling Glomerella Leaf Spot of Apple, 2025

Though Glomerella leaf spot (GLS), caused by Colletotrichum spp., was first identified in Georgia in 1968, it is currently an emerging and significant disease of several apple cultivars grown in the southeastern United States, particularly those with ‘Golden Delicious’ in their genetic background. Fungicide resistance in Colletotrichum spp. has increased recently, highlighting the need for new products or methods for GLS management. Rhyme is a broad-spectrum fungicide containing flutriafol, and it is registered for numerous crops, including apples. A proof-of-concept trial was conducted in 2025 in which Rhyme was applied twice in a soil-injection application, with the hope that it could move systemically and control GLS. However, Rhyme was ineffective; the untreated control generally had similar levels of disease as were observed in Rhyme-treated trees. Therefore, this trial suggests that flutriafol, when applied in soil-injection applications, will not be an effective tool for managing GLS.