Question

The Bordeaux mixture consists of-

• A. Lime and calcium sulphate
• B. Sulphur and lime
• C. Copper sulphate and lime
• D. Copper sulphate and sulphur

Hint:

Remember the ratio style: {CuSO\textsubscript{4} : Lime : Water} = {4:4:50} (vineyard classic). Lime buffers copper to prevent leaf burn.

Answer 1

The Correct Option is C

Step 1: Composition.
Bordeaux mixture is a classic protectant fungicide formed by mixing copper sulphate (also called blue vitriol) and freshly prepared lime (calcium hydroxide) in water.
Step 2: Typical preparations and use.
Common field formulae include 1:1:100, 4:4:50, or 5:5:50 (copper sulphate : lime : water) depending on crop sensitivity and disease pressure.
The lime neutralizes the solution, reduces phytotoxicity, and helps the copper remain as finely dispersed copper hydroxide that adheres to plant surfaces.
Step 3: Why the other options are incorrect.
Lime with calcium sulphate does not provide the fungicidal copper ion needed for action.
Sulphur with lime is a different product (lime sulphur) used mainly against mites and some fungal pathogens, not Bordeaux mixture.
Copper sulphate with sulphur is not the standard Bordeaux formulation and lacks the lime component that buffers copper.
Step 4: Historical note and mode of action.
Discovered in the 1880s for downy mildew control in vineyards, Bordeaux mixture acts as a surface protectant releasing copper ions that inhibit spore germination.
Step 5: Conclusion.
Thus, Bordeaux mixture consists of copper sulphate and lime.