Copper fungicide used to kill blue mold in evergreen trees

Written by barbara fahs
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Copper fungicide used to kill blue mold in evergreen trees
Holly is one of many evergreen plants that copper fungicide can help. (holly image by david purday from

Copper fungicide, often called a "Bordeaux mixture," is a tried-and-true combination of copper sulphate, lime and water. It treats fungal and bacterial diseases, especially blue mould and other types of mildew that affect evergreen ornamental plants and trees, fruits that grow on vines and fruit and nut trees. When you properly prepare this organic formula, it will protect many types of plants against numerous diseases.

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Evergreens That Copper Fungicide Can Help

In addition to the coniferous fir, pine and spruce trees that we commonly call evergreens, copper fungicide is effective on other types of plants that are not deciduous. Included in this group are lemons, limes, oranges and other citrus, all ornamentals, shrubs such as photonics, Italian cypress used in bonsai, holly bushes, magnolia trees, juniper, azaleas and rhododendrons, camellias, jasmine of numerous species, boxwood, Viburnum, palm trees, trailing and vining plants, such as ivy, and many others.

Diseases That Copper Fungicide Prevents and Cures

Among the plant diseases that a spray of copper fungicide can treat are blue mould, which is commonly called downy mildew, powdery mildew, fire blight, leaf curl, shot hole, peacock spot, walnut blight and black spot disease, which affects roses.

Preparing Copper Fungicide

The Bordeaux mixture works best when you prepare it with fresh ingredients, rather than purchasing a ready-made product. For home use, prepare 1 gallon of Bordeaux mixture by combining 3 1/3 tbsp copper sulphate and 10 tbsp of fresh, dry hydrated lime (calcium hydroxide) or slaked lime with 1 gallon of water. This is called a 10-10-100 Bordeaux mixture, which refers to the amounts used for larger applications that call for 4.54kg. of each dry ingredient and 100 gallons of water.

Benefits of Copper Fungicide

In addition to its organic classification, copper fungicide has been successful for decades because it sticks to plant tissue, even during rain. When you use the Bordeaux mixture in fall and winter during plant dormancy, it protects them against diseases that occur after they break dormancy. It's also very effective and long-lasting.

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