They are most effective and are a better choice to use in spring after the trees have broken dormancy and tender leaves are exposed. With all Bordeaux and fixed copper sprays, thorough coverage is essential to give plants the desired protection from disease-causing pathogens. Advantages and disadvantages of both sprays are outlined in Table 1. Advantages and Disadvantages of Fixed Copper Sprays and Bordeaux Mixture. Copper must be kept in dry storage.
Effectiveness is a function of coverage, timing, and concentration.
Because Bordeaux colors the sprayed plants blue and may discolor house paint, it is not used as often on ornamental plants as it is on trees, vines, or agricultural plants. The first number refers to the pounds of copper sulfate, the second number refers to the pounds of hydrated lime, and the last number refers to the total gallons of water to be used. Copper Sulfate . Ordinary lump copper sulfate is not satisfactory because it is slow to go into solution. Store copper sulfate in a dry place.