Besides individual strain characteristics, the main reason is that the relationship between water spraying, ventilation and mushroom production is not properly handled under the high temperature. Generally, in the case of high temperature (19-23℃), after the mulch spraying, the ventilation of the mushroom room is small, the relative humidity of the mushroom room is large, the mycelium growth and development of the material layer and the soil layer are vigorous, the part of the mycelium growth is too high, the fruiting entity is mostly knotted on the surface of the soil layer, the mushroom is knotted densely, and the mushroom transporting water and nutrients from the material layer and the soil layer to supply the mushroom on the surface of the soil layer is far away, so it cannot keep up with the mushroom body's requirements for water and nutrients. Some people call it "balloon mushroom", which results in small and dense mushrooms. In addition, it is also possible that the culture material and the mulch layer are too thin, which may also cause small and dense mushrooms.
 
Prevention and treatment methods.
 
1. After the mulch layer is adjusted to water, firstly, close the door and window to hang the mycelium, make the mycelium hang up to the top of the soil layer, hang to a certain part, spray water after adding fine soil, strengthen ventilation, make the mycelium like hair thick, transform to reproductive growth and twist into mushroom bud in time. 2. When the mycelium in the soil layer is full and the part is moderate, pay attention to strengthen the ventilation and cooling in the morning, evening and night to promote the mushroom, control the mushroom part but not high.
 
2. Pay proper attention to the thickness of culture material and soil layer, the thickness of culture material is generally 15-16 cm and the thickness of soil layer is about 3 cm.
 
If the mulch layer is too thin or the mushroom grows on the surface of the soil layer, you should make up the mud in time and cover with fine soil to artificially lower the mushroom production site to meet the water and nutrient demand of the mushroom body and improve the condition of dense and small mushroom.