Mummy disease

Pseudomonas spp.

The name «mummy» clearly reflects the symptoms of this disease. The affected mushrooms’ base is bulging and has fibrous mycelium around it. The mushroom stipes stretch out and curves slightly. Tilted small caps tighten and open too early. The mushroom tissues harden, and the mushroom’s appearance becomes dry and leathery. Mushrooms affected by the mummy disease never rot. The color of affected mushrooms is grayish-brown. When the mushrooms are harvested, a sound similar to a creak is heard. Mushrooms are pulled out with a big amount of mycelium and casing layer. When a mummified mushroom is cut, a creak also can be heard, the cut become reddish-brown in color.

The mushrooms newly emerging in an area affected by mummy disease don’t develop and remain in a primordial condition.

The disease is able to spread quickly (10-13 cm in 24 hours) in all directions from its source. But since the disease is spread by affected mycelium, the spread of this disease is less noticeable when there is no contact of the diseased mycelium with the healthy one: that is at cultivation in containers, bags and isolated blocks. Due to the fact that the mummy disease is spread by spores, it is less dangerous that a virus. The disease can be transferred from one bed to another only by compost or casing material that contain diseased mycelium.

Mushroom affected by the mummy disease are pulled out with pieces of casing soil

The mummy disease affected mushroom tissue has a brownish shade when broken

Affected mushrooms. Distinctive symptoms: bulging base with fibrous mycelium around it, ...

Affected mushrooms. Distinctive symptoms: bulging base with fibrous mycelium around it, ...

... slightly curved, stretched stipe, and a small, prematurely opened cap.

Mushrooms affected by bacteria that cause the «mummy»

Isolation of the mummy affected area of the bed

The outward appearance of a bed with mushrooms affected by the mummy disease
The pathogenic organisms are bacteria that parasitize in mushroom cells. It is assumed that bacteria enter through the cell walls into hyphae and as a result of their vital activity, the mushrooms’ metabolism is disrupted.

The first symptom of the disease appears in the beginning of fruiting, when some areas of the beds fall behind in their development. The growth of mushrooms slows down and initially stops. The grayish shade of mushrooms and their bad quality also indicate the disease. And even though first diseased mushrooms don’t have changes in their outward appearance (curves), they’re harder to the touch and experienced mushroom growers or pickers can determine the beginning of the infection.

After identifying the disease its source must be localized as soon as possible. For this purpose, a groove is made to the bottom of the bed 1.5 m away from the diseased area; the groove has to be 20 cm wide. Compost and casing layer is carefully picked out and removed from the groove, or laid out on the affected area’s surface. A part of the bed isolated this way is sprinkled with 0.5 % of formalin solution or completely strewed with salt, and then watered. After it’s treated, the area is covered with polyethylene film. If mushrooms are cultivated in containers (bags, blocks), the affected containers are removed, or covered with polyethylene film after treatment described above, so that the diseased mycelium doesn’t contact the healthy one. In the end of the cultivation cycle, the diseased room is thoroughly steamed keeping the compost at a temperature of 70°C for an hour. Wooden surfaces have to be disinfected after steaming.

To prevent the occurrence of the disease, rules of sanitation and hygiene have to be followed. It is assumed that some mushroom strains are more subjected to the mummy disease than others. Therefore, if the disease is recurring, the strain has to be changed. Moreover, it is not recommended to knead the mycelium 24 hours before spawning, because there will be more chances for the disease to enter into the damaged mycelium hyphae. Researchers indicate that the spread of mummy disease is stimulated by overly humid compost and casing layer, especially at high air humidity.