Bob from Eugene, Or writes
My hellebores have black spot. how warm does it ned to be for copper spray to be effective
Per the product label, Bonide Liquid Copper Fungicide Concentrate should not be used on roses in cool damp conditions (under 60 degrees F) due to concerns of phytotoxicity. We recommend following this recommendation for similar flowers as well such as your hellebores. Like most products, Bonide Liquid Copper Fungicide Concentrate should not be used in temperatures over 85 degrees. We usually recommend that you spray early in the morning or in the evening when the temperatures are usually cooler and the product will have time to dry before temperatures reach 85 or above. Spraying in the heat of the day will cause the foliage to burn.
Answer last updated on: 03/18/2020
