This early defoliation can result in weak trees, and if we have a hard winter, trees may be at risk of winter injury. I am not sure of the fungus, but it is likely cherry leaf spot, which causes cherry leaves to defoliate prematurely during the season. Fung-onil Multi Purpose Fungicide Concentrate. Bacterial leaf spot. Ferti-Lome Broad Spectrum Landscape and Garden Fungicide. Ferti-lome Liquid Systemic Fungicide II. The disease mainly affects the leaves, but lesions may also appear on fruit, petioles and fruit stems (pedicels). Cherry leaf spot is one of the most serious diseases of both sweet and sour cherries in the Midwest. This common plant disease can affect nearly any plant in your garden, but if you have stone fruit trees in your garden (think cherry, plum or apricot), then you need to be especially aware of this plant disease. Hello. Learn how to control Cherry leaf spot with these easy to use products! 1. Diseased leaves drop prematurely, and severely affected trees may be … Products labeled to treat Cherry leaf spot; Bonide Fruit Tree Spray Concentrate.