Is it for your tomatoes Westi.
If so this might help (copied from a American website and turned into English
Plan to spray tomato plants with copper sulphate fungicide on a cool, calm day. Don't apply copper sulphate on a very windy or rainy day.
Put on a long-sleeved shirt, trousers and eye goggles before spraying copper sulphate. This chemical can cause skin and eye injury.
Fill a hand sprayer with 1 gallon of water and 4 teaspoons of copper sulphate. Mix thoroughly.
Attach a hollow-cone nozzle to the hand sprayer for best application results. Hollow-cone nozzles spray medium-fine 0.01-inch droplets that cover the plant thoroughly.
Spray tomato plants with copper sulphate two to four weeks after transplanting them into your garden. Cover the plant stems and the tops and bottoms of leaves with the spray. The fungicide helps prevent blight, nailhead rust, bacterial spot, leaf mould, Anthracnose, Stemphyllum leaf spot and Septoria.
Repeat the copper sulphate application again every seven to 10 days. You will need to apply the fungicide more often in humid or wet weather.
This may also helphttps://www.rhs.org.uk/advice/pdfs/fung ... -gardeners