Casing And Recasing
When one or more jars have been completely permeated by mycelium, one can move on to the fourth step in the process that leads directly to the productionof mushrooms. In commercial mushroom culture, this step is called rasing. In the method outlined here, casing consists of removing the dome and band lid of the jar, and covering the surface of the permeated rye with about Vi to 34 in. (Vi cup for quart jars) of sterilized soil (fig. 40 & 41). The soil should be premoistened to field capacity before being applied. The fastest way to do this is to spread the soil on a clean sheet of plastic and spray it lightly with the spray nozzle of a garden hose. Mix thoroughly. Field capacity can be gauged by the following rule of thumb: spray the casing soil just enough so that the soil is moistened throughout, but no water passes through the soil into the mycelium. In other words, moisten thoroughly, but do not saturate the soil. If the soil is to be sterilized, it should be moistened first. After sterilization, it can beconvenientlystoredina double layer of plastic garbage bags, after it has cooled. Small amounts of casing soil may be dampened by putting two or three liters of casing soil in a large mixing bowl and moistening it with a pump sprayer. A large wooden spoon is perfect for folding the wet layers of soil into the dry. Alternate spraying the soil and stirring the dampness throughout the mix. When the casing soil has uniformly darkened in color and retains a shape when squeezed, it is ready to use. Once in the jar the soil should be shaken level and wetted a bit more with a fine mist sprayer (fig. 42 & 43). A fine-mist spray must be used to avoid sealing the surface of the casing soil.
After applying and moistening the casing soil, discard the lids and maintain the cultures in a high humidity environment. A large styrofoam cooler with a window cut into the lid and covered with clear or translucent polyethylene is excellent for this (fig. 17-20), so is a glass aquarium. If maintaining the jars in aquaria or styrofoam boxes, it is important to pay attention to proper aeration. Experience has shown that the daily transpiration/evaporation cycle is important if oneis tohave vigorous fruiting, healthy cultures. Maintaining the proper moisture balance and evaporation rate in the casing soil is actually a complex interplay among temperature, aeration, and evaporation. If either temperature or aeration isexcessive, the soil will dry out. On the other hand, it should not become waterlogged, and a minimal amount of air movement should be present to facili ta tea slow, even rate of evaporation from the casing soil For this reason we recommend incubating the boxes with the lids partially or wholly removed after fruiting has begun. The temperature should be kept above 70 degrees F. Spray the cultures daily with a fine-mist spray just enough to make up for moisture lost through evaporation (fig. 44). Each cased jar requires 2-3 good squirts of water per day to maintain continuous fruiting. Do not exceed field capacity. A good test for proper moisture content is that the surface of the soil should feel moist and spongy to the touch. Boxes of newly cased jars should be stored in chronological order.
Watering becomes a critical matter at this stage. If the correct water level is maintained in the casing soil, the first flush of mushrooms will be normal. But if jars are allowed to become too dry, then aborted fruiting or formation of many small mushrooms unable to grow to full maturity will occur. With proper watering and proper aeration, perfectly normal first flushes can be grown. What is a proper amount of moisture? The general tendency seems to be for beginning cultivators to keep jars too dry. Remember always to use premoistened casing soil. Make sure the distribution of the moisture is uniform. Once jars have been cased with pre-dampened soil, they ordinarily only need water once a day. The exceptions occur during and after periods of intense fruiting when slightly more water is required, orduringspells of dry, hot weather. Strong drafts, especially warm drafts from floor heaters, can dry jars out very quickly. If one keeps jars on shelves that are open to the surrounding room part of the day, then it is especially important to keep the heaters from blowing directly on jars. Shelves can be enclosed in transparent poly u ret ha ne film in order to maintain high humidity and minimize contamination.
The other extreme to a void is overwatering. The casing layer should be kept damp but not soaked. Any visible water accumulating between the rye covered mycelium and the walls of the jar indicates overwatering and a potential for contamination. Often if left unattended such jars become yellowish, indicating a more advanced
fig. 41: Vi cup casing soil is applied.
fig. 41: Vi cup casing soil is applied.
stage of contamination. Such jars should be placed on a shelf together—separate from the other jars—and all water should he withheld until excess water in the jars recedes completely. Often, upon recasing, such jars seem to regain their equilibrium, and fruiting, though delayed, is normal.
During the next two to three weeks, the mycelium will begin to grow up into the casing soil, penet rating it to just beneath the surface(fig. 45).ThemyceIium mayoccasion-ally break out onto the top of the soil and begin to spread across its surface, and part of the purpose of spraying daily is to keep this surface growth "knocked down" with the spray (fig. 46). Excessive surf ace growth, in which the mycelium completely overgrows the casing soil and formsa thick spongy crust on thesurface, isanindication that the mycelium is starved for air and that ventilation should immediately be increased. If you are under-watering your jars, this surface mycelium will turn blue with thirst. As the mycelium grows into the casing soil, it will begin to form a network of ropy strands visible at the interface of the soil and the glass. This network gradually gains more and more intersecting nodes, and by the 14th to 20th day after casing, these nodes have differentiated into tiny white dots distributed through the casing soil along the perimeter of the jar. These dots are the young mushroom primordia; gradually they enlarge and incorporate more mycelia, slowing takingon theappearanceof tiny mushrooms with squat, fat stems and dark, brownish heads. This is the"pin" stage in the development of the mushroom and the primordia at this stage a re a bout 1-2 mm in length. These pins continue to enlarge and some will begin to thrust above the surface of the casing soil, both at the sides and in the center of the jar. Once the young mushrooms have penetrated the surface of the casing soil, another five totendaysisrequiredforthemto reach full maturity. At maturity the mushrooms may be 2 to 9 inches tall and have caps ranging from 1 to 3 inches in diameter (fig. 47 & 48). We have also found that these mushrooms do respond favorably to light, and that a daily 13-hour fluorescentorGrow-luxcycleresults in mushrooms with larger caps and shorter stems than those grown without any special lighting. Probably it is not advisable, however, to place the cultures in direct sunlight for prolonged periods. While many mushrooms will grow to full size, approximately an equal number will grow to about half-size or less and then cease to grow; these "aborts" can still be plucked, dried, and used, although they are not as aesthetically appealing as the fully matured specimens. With practice one can learn to spot aborts early and remove them from thecultures. Aborted mushrooms left in the cultures are susceptible to attack by bacteria which quickly render them both ugly and unusable.
Excessive numbers of aborts are another indication of inadequate aeration. If the jars are being incubated in styrofoam boxes or aquaria, there is a possibility of accumulating carbon dioxide in the air space above the casing soil. This will inhibit fruiting and/or prevent fruits from reaching maturity. If thishappens, increaseaerationby leaving the lids off the box, or by using a small fan to enhance air movement over the surface of the jar. Be careful not to over aereate, however; too fast a rate of evaporation will cause the casing soil to dry out.
Occasionally mushroom primordia will form down toward the bottom of the jar and grow to maturity but will not break the surface of the casing soil. It is possible to inhibit this effect somewhat by wrapping jars with tinfoil to the top of the casing soil (fig. 45). This effect, formation and development of primordia toward the bottom of the jar, is normally seen during the earliest mushroom "flush." After the first flush, the jars are recased for each subsequent flush (see below). We find that recasing will largely eliminate this problem for all flushes but the first one.
A variety of types of casing soils have been found to effectively promote fruiting. We have found the following mixture to be one of the best:
7.5 liters peat moss 3.5 liters fine vermiculite 4 liters washed fine sand
2 liters calcium carbonate (finely crushed oyster shell)
Powdered oyster shell is sold as a feed supplement by many feed companies. The calcium carbonate is an optional ingredient and can be left out without significantly affecting fruiting. It should be added if available, however, to buffer the soil and keep it from becoming too acidic. This factor way contribute to the growth of con taminants on the surface of the casing soil, and the calcium carbonate can inhibit or prevent this. For thesame reason, one may also wish to water occasionally usinga saturated solution of calcium carbonate. We have also found that a mixture of one part mica-peat (50/50 vermiculite-peat-moss mixture) to one part potting soil will work.
Sterilization of casing soil is usually recommended but we found it unnecessary when relatively sterilecommer-cially bagged materials were used. If you wish you may sterilize casing soil before use at 15-20 lbs. pressure for 30 minutes. It should be wetted firsttofieldcapacity.Casing soil can be stored indefinitely in a tightly sealed large glass jar, or in a polyethylene garbage bag. If a glass jar is used, it can be sterilized with the casing soil in it. Remember to loosen the lid prior to sterilizing. After the first flush of mushrooms, the soil and mycelium-covered block of grain will shrink somewhat, leaving a space between the mycelium and the walls of the jar. Whenever this condition is noticed, it is time to recase. Recasing will greatly extend the life and fruiting capacity of your jars. It is a simple procedure which involves using a clean fork (one per jar, as this way contaminants are not spread from jar to jar) to scrape off all of the old casing soil and aborted mushrooms growing down along the sides of the jar. Then, using fresh casing soil prewetted as before, recover the mycelial block and use the fork to work the fresh casing soil down the sides of the jar around the block as well as covering the top. It will take yourjars about twoweeks to recover from this treatment but then they will do their best fruiting, producing clusters of large carpophores and behavingas if this recasing procedure had made them more resistant to contamination.
Instead of applying the casing soil to the mycelia-covered rye in the jars as described in the preceding pages, it is possible to adopt a somewhat different approach to the making of cased cultures. The steps involved in this method are described briefly below. The basic idea for this method was suggested to us by a friend, Paul Kroeger, and his contribution is gratefully acknowledged. In order to use this method, one begins by growing the mycelium out on the rye in the Mason jars in exactly the manner described above for the cased jar method. One may use plastic trays, glass baking pans, or one may ma nu fact urea styrofoam box with a window of clear plastic in the lid as described above (fig. 17-20). Sterilize the inside surface of the tray or box thoroughly by wiping down with a 25% Clorox solution followed by a Lysol spray. Cover the bottom of the container with a 34-l inch-deep layer of perlite or a 1:1 mixture of vermiculite and casing soil. Grow the mycelium on the rye medium in the Mason jars until it is fully permeated and ready to case. Instead of casing at this stage, however, shake the jars again. The mycelial block will be tightly woven together and may require a little extra effort in order to be shaken loose. After shaking, empty the contents of several jars into the container so as to form a layer of rye "spawn" a bout 1-1 Vz inch deep.
The number of jars required to do this will vary depending on the size of the container, but usually between five and ten jars are sufficient. Cover the rye layer with a second layer of moistened casing soil, to a depth of 1-1 Vi in. One has now created a 3-layered"sand-wich" arrangement in the container: Perlite or vermiculite-casing soil forms the bottom layer and provides drainage; the second, rye and mycelium layer provides the nutritive substrate for the mycelium; the topmost, casing layer prevents the mycelium from becoming desicated or attacked by contaminants as well as functioning to induce the mycelium to fruit. Once the layers have been made, maintain the container in a humid environment and as close to 70 degrees F. as possible. If using sty-rofoam boxes, keep the lid on for the first two weeks following casing. Since the soil is moist and the mycelium produces water in its respiration, humidity willbehigh in the box (in fact, condensation on the transparent lid can usually be seen) and therefore one should not spray, or should spray only lightly and infrequently, during this stage.
Two weeks after casing, or approximately one week prior to the commencement of fruiting, the lids should be removed to prevent carbon dioxide accumulation in the containers. Daily watering with a fine mistcan bestarted after the lids have been removed. The mycelium will continue to grow into the casing soil. Fruiting, at both the sides and center of the container, will commence 21-30 days after casing. The box or tray culture will fruit abundantly, producing many clusters of perfect large carpophores in various stages of maturity across the entire surface of the casing soil. As these clusters are plucked, the holes created in the casing soil should be plugged with fresh casing soil. Recasing as described for the jars is not necessary with this method. The container cultures will usually succumb to con tarn ¡nation (usually a green mold which shows up on the surface of the casing soil) more quickly than the jars. Containers fruit for30 to 40 days as opposed to 60 to 80 days for jars, but the flushes produced during this time are so abundant that the overall total yield for trays and jars is comparable (approximately 10 grams dry weight of mushroom for every 100 grams dry weight of rye).
When your cultures are well established in the mature fruiting phase, it is a good idea to shift your awareness toward a new class of potential pests and carriers of contamination. These are insects, specifically flies and mites. The best way of controlling flies is by keeping your cultures in a screened room that flies are unable to penetrate. Even in the most tightly sealed environments flies do occasionally occur. It is therefore a good idea to use a slow acting insect killer of the vaporizing type, such as the"No-Pest Strip" in the growing area. Usually this is all the fly protection that is necessary. Mites are a more persistent and difficult pest to control. Massive reliance on applied insecticides is the commercial mushroom growers'approach to mite control. But we believe that application of insecticides to Stropharia cubensis should be undertaken only as a last resort.
The real key to mite control is early detection. Therefore, examine your jars very carefully. Mites are most visibly active in the middle and late afternoon, and are usually first spotted wandering around on the smooth rim of the jar. They are tiny specks, distinguished from tiny bits of casing material only by their mot ion. Jars with mites should be immediately isolated, or preferably removed entirely from the growing area. Once mites are detected, the grower must go to a state of high alert and check the jars every day to see if the plague is spreading. Removal of infested jars is the best course. The next best course is to spray only the infested jars with a V4-strength solution of Malathion. Malathion, though anathema to the anti-insecticide purist, is one of the least toxic and most rapidly degraded of commercial insecticides. It should not, however, be used on cultures within6 daysof fruiting. Under no conditions should the miticideKeldane be applied to cultures. Keldane is FATAL to Stropharia cubensis.
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