What Types of Physiological Deformities Occur in Mushrooms? A Full Analysis of Common Types

Mushroom deformities are mostly triggered by temperature differences or unfavorable environmental conditions; they may also be related to the strain used. The common deformed mushrooms mainly include the following types:

1. Hollow stipe. From the outside the mushroom looks normal, but when the base is cut off, part of the stipe is found to be hollow, usually with a ring-shaped cavity around a hard core. Afterwards, the cut surface of the stipe may split and curl backward, making the mushroom poor in appearance and reducing its marketability.

Cause: This is mainly caused by low air humidity during the fruiting period, rapid evaporation of water from the mushroom body, and overly dry casing soil, so that the fruiting bodies cannot obtain water.

2. Split stipe. The stipe splits vertically, sometimes accompanied by horizontal splitting, causing the stipe segments to curl upward and downward.

Cause: The mushrooms first grow in very moist casing soil, then the casing soil dries, and then the casing soil humidity is rapidly increased again, inducing the split symptoms.

3. Swollen stipe. Occasionally mushrooms are seen with a swollen stipe, which may be at the base, the middle or the top of the stipe.

4. Hard gill disease. Diseased mushrooms with opened caps. Viewed from below, the color is pale, and the gills are very shallow or absent. If the cap splits, the cap usually appears thicker than normal.

5. Malformed mushrooms. The differentiation of the fruiting bodies appears blurred and indistinct, and this is often associated with the first flush of autumn. They fail to develop normally and turn into various malformed mushrooms, ranging from nodular forms to fruiting bodies whose shape can still be roughly distinguished but whose caps are oddly shaped. Individual fruiting bodies may also be joined together.

6. Water-soaked disease. The symptoms of affected mushrooms are clearly visible water-soaked areas, especially on the stipe; if the mushroom is squeezed, water comes out; and sometimes mature fruiting bodies spontaneously exude large amounts of clear or colored liquid and then rot.

7. Cryptic dry rot. The symptoms are similar to dry rot, but the mushroom can resume growth and produce normal fruiting bodies. It is caused by long-term excessive watering.

8. Clustered pinheads. Large numbers of small pinhead mushrooms are produced, and basically none of them can develop and grow larger. This occurs when pinheads form under conditions that are overly favorable.

9. Clumped mushrooms. Clumped mushrooms refers to mushrooms fruiting in clumps, which is related to periodic low temperatures at the time of pinhead formation.

10. Mycelial mat. After the mycelium has grown through the casing soil, a thick layer of white mycelium forms on the casing surface. The mycelial mat is impermeable to water, and fruiting is hindered. This is caused by high carbon dioxide concentration combined with high humidity and high temperature. In addition to adjusting the environmental conditions, the remedy is to lightly scratch the surface immediately when the mycelial mat first appears and cover it with a fresh layer of casing soil.

11. Death of pinheads. This generally occurs in a later flush; the casing soil colonizes well with mycelium, yet the pinheads die and no mushrooms are produced in the patch.

Cause: It is usually caused by a water-impermeable mycelial layer in the casing soil, which leads to water pooling on the casing surface. Opposite to mycelial mat disease, the cause is insufficient watering in the early stage of mushroom growth, so that dense mycelium colonizes the dry casing soil.

12. Soil-covered mushrooms. When mushrooms fruit in casing soil that is too deep, they are often wrapped in casing soil.

Cause: Mistimed fruiting or drying of the casing surface causes deep fruiting.

13. Scaly mushroom bodies. The scales on the surface layer of the mushroom body lift up.

Cause: A natural response to dry air or fumes of sodium pentachlorophenate from the mushroom bed.