Step-by-Step Guide to Fix Oyster Mushroom Contamination Issue?

Step-by-Step Guide to Fix Oyster Mushroom Contamination Issue?

The contamination in your mushroom bag appears to be caused by black mold and poor mycelial growth. Here’s how you can fix the current problem and prevent it in future batches.

A. Immediate Actions to Fix the Current Issue

1. Identify & Isolate Infected Bags

✅ Remove the contaminated bags from the growing area immediately to prevent mold spores from spreading.

✅ If only a small area is affected, you may cut out the contaminated part and treat the bag (explained below).

✅ If the bag is heavily infected, discard it completely.

2. Improve Airflow & Reduce Humidity

✅ Increase ventilation by using exhaust fans or opening vents to reduce humidity.

✅ Keep humidity levels between 75-85%.

✅ Avoid direct water spraying on substrate bags. Instead, spray mist in the air.

3. Treat the Contaminated Bags (If Salvageable)

🔹 Hydrogen Peroxide Solution:

Mix 0.5% hydrogen peroxide (H₂O₂) with water.

Spray lightly on the infected area. It kills mold but does not harm mycelium.

🔹 Lime Water Spray:

Mix 1 teaspoon of hydrated lime in 1 liter of water.

Spray on the contaminated area to create an alkaline environment that prevents mold growth.

🔹 Salt Treatment (For Small Infected Spots):

Apply table salt directly on mold patches.

This will dehydrate the mold and stop its spread.

4. Check Moisture Levels

✅ The substrate should be moist but not soggy. If excess moisture is visible, let the bag dry slightly before misting again.

✅ Avoid overwatering, as standing water promotes mold growth.

B. Prevent Future Contamination

1. Use High-Quality Spawn

✅ Always buy spawn from a reliable supplier to ensure it is free from contamination.

✅ Before use, check if the spawn has any black, green, or slimy patches—these indicate contamination.

2. Properly Pasteurize or Sterilize Substrate

✅ For pasteurization:

Heat the substrate to 60-70°C for 4-6 hours.

This kills mold spores while keeping beneficial microbes intact.

✅ For sterilization:

Use a pressure cooker or autoclave at 15 PSI for 1.5–2 hours for a fully sterile substrate.

3. Ensure Good Ventilation

✅ Install an exhaust fan or use natural airflow to keep the air fresh.

✅ Do not overcrowd the bags, as stagnant air can lead to mold formation.

4. Maintain Proper Hygiene

✅ Wash hands and sanitize tools before handling spawn and substrate.

✅ Clean the growing room regularly with disinfectants to prevent mold buildup.

5. Use Antifungal Treatments (If Needed)

✅ Adding neem oil or cinnamon extract to misting water can help prevent mold naturally.

✅ Some farmers also use Trichoderma or Bacillus subtilis-based biofungicides for prevention.

Final Check: How to Know If Your Mushrooms Are Safe?

✅ Healthy mycelium should be pure white, fluffy, and evenly spread.

❌ Moldy mycelium will have black, green, or slimy patches and may emit a foul odor.

If you still notice mold returning even after following these steps, the issue may be deep contamination in the substrate or spawn, requiring a complete restart with fresh materials.