Why Is Bordeaux Mixture Preferred in Organic Farming?

As modern agriculture shifts toward safety, sustainability, and eco-friendliness, Bordeaux mixture (Boóc-đô) has gained renewed attention—especially in organic farming.

So why has this classic fungicide maintained an important role for over 140 years, and why is it accepted under strict organic standards like VietGAP, GlobalGAP, and EU Organic? Let’s find out.

1. What Is Bordeaux Mixture?

Bordeaux mixture is a fungicidal preparation consisting of:

• Copper sulfate (CuSO₄)
• Hydrated lime (Ca(OH)₂)
• Water

It is a contact fungicide with a broad preventive spectrum, effective against many crop diseases such as anthracnose, downy mildew, rust, powdery mildew, and leaf spots.

Invented in France in the 19th century, it was the first chemical plant protection product used successfully against fungal diseases.

2. Why Is Bordeaux Mixture Allowed in Organic Farming?

✅ Mineral-based – not synthetic chemicals

• Contains no petroleum-based derivatives, synthetic chemicals, or GM ingredients.
• All components are naturally occurring minerals, permitted in organic input lists.

✅ No harmful residues when used correctly

• Although it contains copper, residues do not accumulate dangerously if applied within recommended limits.
• Respecting pre-harvest intervals ensures compliance with international MRLs (Maximum Residue Limits).

✅ Fits the organic principle of “prevention over cure”

• Bordeaux mixture is contact-only, not systemic, so it doesn’t affect plant tissues internally.
• When applied preventively (e.g., early rainy season), it protects crops against fungal outbreaks—aligning with organic practices that emphasize disease prevention.

3. Accepted in Organic Standards

👉 Typically, copper application is restricted to 4–6 kg Cu/ha/year (depending on the standard).

4. Practical Effectiveness in Farming

🌿 Diseases prevented by Bordeaux mixture:

• Downy mildew, late blight
• Anthracnose, scab, leaf spot
• Powdery mildew, rust, blight
• Some bacterial rots (indirect effect)

📌 Effective crops:

• Fruit trees: citrus, mango, durian
• Vegetables: tomato, cucumber, chili
• Industrial crops: coffee, pepper, tea, rubber
• Grapes: highly effective for downy mildew & powdery mildew

5. Advantages vs. Synthetic Fungicides

6. Usage Notes in Organic Farming

• Do not exceed the annual copper limit to prevent soil accumulation.
• Avoid spraying in strong sunlight or on tender shoots to prevent leaf burn.
• Do not mix with synthetic pesticides or foliar fertilizers.
• Alternate with biological products (e.g., Trichoderma, Bacillus subtilis) for better integrated protection.

7. Conclusion

Bordeaux mixture remains one of the few fungicides permitted in organic agriculture because of its natural mineral composition, broad-spectrum activity, and safety when applied correctly.

As a preventive shield against fungal diseases, it deserves a place in farmers’ Integrated Pest Management (IPM) programs—helping achieve clean, sustainable, and export-ready produce.

👉 For organic and eco-friendly growers, Bordeaux mixture is not just a tradition—it’s a proven, practical solution for long-term crop protection.