You have started cool down, but the mycelium fails to develop properly in the casing soil. The surface of the casing soil stays black. The pinheads develop from the mycelium below and between the clumps of casing soil and are therefore invisible. In these growing rooms too many pinheads then develop, which will lead to lower quality and fewer harvesting days.
What is the cause?
I can give you three reasons for this:
• As you are unable to see the pinheads, you fail to slow their growth and maintain a temperature.
• The casing soil is not white, which means that there is less mycelium on the surface. Mycelium blocks the evaporation of the casing soil. Without mycelium there is higher evaporation, and therefore more pinhead development.
• The pinheads are between the clumps of casing soil and therefore well protected by the microclimate, with the room climate (macro climate), you have less influence and the pinheads will all grow out.
What action can be taken?
If the mycelium fails to develop properly during the first two days, reduce the RH and CO2 more gradually. This will stimulate more mycelium growth. This helps, but only to a limited extent. In addition, if the casing soil still shows black during pinhead development, look between the clumps of casing for pinheads. You are sure to find some! If you use a higher temperature (e.g. 0.5oC higher than normal) during pinhead development, you will notice the number of pinheads will fall.
Bron: mushroom blog Mark den Ouden