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Greenhouse - The Mushroom

( Originally Published 1920 )

Cultural Considerations. As a rule florists are not as yet giving the mushroom the attention and consideration which it deserves. It is a crop which adapts itself particularly well to growth under benches, so that it utilizes all the extra greenhouse space (fig. 32, a and b.). Like all other remunerative crops, it requires skill to insure its permanent success.

Temperature. Mushrooms may be grown in tomato houses. In this case, the day temperature should run from 6o░ to 700 F. and the night temperature about 55░ F. It should never be allowed to fall below 5o degrees. At less than 5o░ the crop does not thrive, although the spawn in the soil may endure freezing temperature without being killed.

Preparation of Soil. In preparing the soil, fresh horse manure is mixed with loam as follows : To three shovelfuls of manure add one of loam, piled alternately in thin layers. This is kept for three days, but mixed every day in order to prevent the rapid fermentation or heating. This mixing is continued until all danger of spontaneous combustion is over. At this stage, the manure loses its rank odor and is ready to be put in the bed.

Preparation of the Beds. The beds should be located preferably under the center benches, and inclosed in rough boards eight inches wide and one inch thick. The boards are set on edge and raised slightly above the floor so that with a bed ten inches thick the top of the bed would not extend much above the upper edge of the board. A layer of pre-pared manure is then spread evenly over the bottom of the bed, to the depth of three inches, and firmly pressed down by pounding with a brick. Two other layers of manure, each three inches thick and firmly pressed down are laid on the first, making the bottom about eight inches thick. A thermometer is placed in the manure and the temperature watched until it registers about 90 degrees F.

Spawning the Bed. When the temperature of the manure in the bed ceases to rise above 90 degrees, it is ready to be planted with the spawn. The latter is usually bought in bricks, sixteen of which make a bushel. Each brick is broken into twelve equal parts, which are inserted about an inch deep in the manure bed with intervals of nine inches. The manure is then packed firmly over the pieces, leaving the surface of the bed smooth again. Two weeks after planting the spawn, the beds are coated with two inches of the mellow loam prepared as stated above. The loam should be neither dry nor wet, but simply moist. It should not be applied until it is certain that the spawn has commenced growing. This becomes noticeable as a bluish-white, moldy growth. The loam beds should be covered with a three-inch layer of excelsior to keep them from drying. The mushroom beds should be protected from the drippings of the overhead benches by a roof of heavy waterproof cover.

Watering. Care should be taken never to over water the beds. It is necessary to apply enough water to keep the surface of the bed moist, but not soaked. In watering the excelsior is often rolled back - or else water may be applied on top of it. Beach* recommends as the beds begin to bear that they be watered twice a week with nitrate of soda dissolved at the rate of one ounce to each gallon of water. It is applied with a watering can in a quantity sufficient to moisten, but not to soak the beds. To promote good bearing and to prevent a rapid exhaustion, the beds are often coated over again with a layer one and a half inches thick of fine mellow loam.


Mushrooms are subject to few diseases. There are but two which need concern the greenhouse man.


Caused by Pseudomonas fluorescens (FI.) Mig. This disease, although serious, seems to be restricted as yet to the mushroom caves in St. Paul, MinnÚsota. The trouble was first described by Tolaas.*

Symptoms. It is characterized by an unsightly spotting of the caps, the severity of which differs in the cultivated varieties, especially the large white kinds. The spots, which do not extend deep into the flesh, appear while the mushroom is in the but-ton stage, or when the cap is fully expanded. The spots are at first pale yellow, but later become a chocolate brown. Though the disease does not seem to reduce the yield, the market value of the spotted mushrooms is considerably reduced.

The Organism. Pseudomonas fluorescens is a small rod rounded at both ends and motile by means of polar flagella. It is a facultative anaŰrobe; produces no endospores, no gas, but liquefies gelatine. On beef and potato agar, it produces a shiny grayish white growth accompanied by a greenish pigmentation, which diffuses in the substratum.

Control. Spraying the mushroom caps with solutions of benetol, sodium carbonate, or copper sulphate seems to have no beneficial effect. On the other hand, fumigating the beds with sulphur before planting the spawn insures the production later of a clean crop of mushrooms. The amount of sulphur to use is about one and a half pounds to each thou-sand cubic feet of house space.

Caused by Mycogone perniciosa Mag.

The Mycogone is a very destructive mushroom disease. The exact amount of its distribution in the United States is as yet unknown. However, if once introduced in a house, it is likely to ruin the en-tire crop.

Symptoms. The symptoms of the disease are often various. The presence of the malady may be indicated by small tubercules on the cap and by a form of fluffy white growth on the gills, which interferes with their normal development. The result is distorted caps and stipes, and finally, a general darkening and decay of the tissue. In severe cases, monstrous soft masses with thick white fungus coatings are observed in houses in which the disease is very prevalent. In this case, the affected plants have little resemblance to mushrooms. They decay rapidly, and emit a very disagreeable odor.

The Organism. The spores of Mycogone perniciosa are very characteristic. They consist of two cells, the upper spherical, rough, and covered with warts, the lower hyaline and smooth. Both cells possess thick walls.

Control. According to Veihmeyer, there are no evidences that tend to show that the Mycogone disease is carried with the spawn manufactured by the "tissue culture" method. It is very probable, how-ever, that the disease was introduced into this country from France with imported virgin spawn collected at random from fields. The disease may be introduced into a new place with the manure and then spread quickly in a number of ways. Immediate precautionary measures are essential for the control of this trouble. Diseased plants when first noticed should be pulled out and burnt. Allowing these infected plants to decay in the beds is a sure means of spreading the fungus broadcast. The gain from keeping the beds free from diseased specimens will more than compensate for the trouble. At the end of the season the soil in beds should be carried away to a distance where mushrooms will not be grown, al-though it may be used for garden purposes, since the Mycogone disease is known to attack only mush-rooms. After the house has been thoroughly cleaned out, it should be disinfected with the formaldehyde gas method. This is carried out as follows: For every thousand cubic feet of house space use three pints of formaldehyde and twenty-three ounces of potassium permanganate. The potassium permanganate is placed in two or three earthen or wooden vessels, each having a capacity of one quart to every ounce of permanganate. When ready for the operation, the mushroom house is sprinkled with water, the potassium permanganate placed in the receptacles, the formaldehyde is poured evenly over the permanganate, and the greenhouse doors are closed at once. They are kept closed for twenty-four hours and then opened to allow the formaldehyde fumes to escape. All lights must be kept away from the house while they are being fumigated since formaldehyde gas explodes upon coming in contact with fire. Mush-room houses thus treated may be thoroughly rid of the Mycogone disease, but care must be taken to prevent reinfection.

It is hardly necessary to add that all tools and wagons which were used in connection with the infected houses should be disinfected before being used again. All such tools and vehicles should be washed in a solution of one pint of formaldehyde in twenty gallons of water. Throughout the process the operator must exercise extreme care not to inhale any of the poisonous formaldehyde fumes.

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