Key Points on Proper Piercing for Ventilation During Shiitake Mushroom Mycelium Development

Piercing for ventilation during the mycelium development phase of shiitake mushrooms helps increase oxygen levels in the substrate, expel waste gases released by the growing mycelium, and accelerate its growth. This shortens the time needed for the mycelium to reach physiological maturity. Correct and reasonable piercing is one of the important measures to ensure high-quality, high-yield shiitake production in autumn and winter bag cultivation.

1. Characteristics of Oxygen Deficiency
Mycelium growth slows down. The tips of the mycelium become thinner and uneven. Lumps or nodules may form. These symptoms indicate a lack of oxygen within the substrate bags, and piercing for ventilation becomes necessary.

2. Piercing Methods
First Piercing: When the mycelium circle has a diameter of about 10 cm: For bagged cultivation with sleeves, remove the sleeves. For bags without sleeves, pierce 4–6 holes around 2 cm inside the edge of the mycelium circle.

Second Piercing: When the bag is fully colonized by mycelium, typically 40–45 days after inoculation: Pierce on the side opposite the inoculation site. Keep the holes shallow, 1–1.5 cm deep, and create 20–30 holes per bag. This phase involves minor ventilation. Avoid large or deep holes or excessive hole numbers to prevent dehydration, which may hinder lump formation and primordia development.

Third Piercing: 7–10 days before removing the bags: This phase involves major ventilation. Holes should be 2 cm deep, with 40–60 holes distributed across the entire bag.

3. Precautions
The number and depth of holes affect oxygen levels, moisture content, and temperature within the substrate. Adjust these based on specific conditions of the substrate and environment. After piercing, reduce the stacking density per unit area. Arrange bags in a triangular (“△”) shape instead of a grid (“井”) to prevent excessive temperature rises, which could overheat and damage the mycelium.

4. Misconceptions About Piercing
Many growers mistakenly believe that piercing should only occur after lumps or nodules appear on the substrate bag. However, the best time for piercing is 5–7 days after the mycelium fully colonizes the bag—before lumps form. Lumps usually result from a combination of high temperatures and oxygen deficiency. If lumps have already formed, the mycelium is already oxygen-starved. Piercing at this point can injure the mycelium, increasing the risk of "red water" leakage. To avoid such issues, pierce as soon as lumps begin to form or, ideally, beforehand.

5. Key Considerations for Piercing
Ensure Full Mycelium Colonization: Piercing bags not fully colonized by mycelium increases the risk of contamination. Isolate uncolonized bags for separate management.

Prevent Cross-Contamination: Infected bags should be handled separately to avoid spreading contamination during piercing. A single infected bag can affect several others.

Temperature Management Post-Piercing: After piercing, the mycelium becomes more active and generates heat. Maintain temperatures around 25°C, and do not exceed 28°C to prevent overheating or damage to the substrate.

Effective management of temperature before and after piercing is critical to ensure substrate survival and success. Controlling temperature during this period is the key to achieving high survival rates. Once temperature is well-managed, success is within reach.