Miesięczne archiwum: Maj 2014

09.2014 Problems of the third flush

Two mechanisms of mushroom feeding were considered in the implementation of the concept of controlled mushroom feeding. The first mechanism refers to a direct feeding by the enzymatic degradation of dead organic substances when the obtained nutrient ingredients are collected in the mycelium. Their amount plays a significant role in the production process and affects the yield in the first and second flush.

The second mechanism is the indirect feeding, consisting of the absorption from the compost easily soluble nutrients produced during the cold composting (commensalism). Thus, nutrients dissolved in water are transported through the mycelium to the fruiting bodies and therefore affect the yield in the third and fourth flush. The change of the feeding method results in substantial yield decrease. The average yields from these flushes do not exceed 5 kg/m2. This situation raises the question as to whether the yields in these flushes, particularly the third one can be increased up to 10 kg/m2. Two hypotheses were examined. The first one assumes that yield gain can be achieved through an increase of nutrient stocks during the direct feeding. It should guarantee the yield at the level of 40 kg/m2 in two flushes and additional 5 kg/m2, which in total could provide the yield of 50 kg/m2 in the third flush. So far this concept has failed. An increase of nutrient stock could not be balanced efficiently with water, which was required to complete requirements of higher dosage of corn feeder. The compost was not able to absorb more water therefore the increase of water amount could have resulted in compost decay. Not balancing water needs caused a yield reduction due to the drying out of compost. The obtained result was opposite of the planned goal as the yield in the third flush decreased. As the second flush yield increased above 17 kg\m2, a short-term retention of fruiting body growth occurred on the casing surface and caused a delay of their emergence from the deeper layers. This situation resulted due to the dying out mycelium on the casing surface during the second flush that was caused by the casing drying out. The production stabilized yielding (5-6 kg/m2) in the fourth flush when the fruiting bodies developed normally. Regarding this situation the second hypothesis of using a standard amount of corn feeder was tested. This approach assumes that the yield can be increased by an addition of monosaccharides and citric acid into casing. Also, in order to stimulate the growth of fruiting bodies an effect of changes of microclimate, mainly lowering an air temperature would enhance growth of fruiting bodies allow the obtained generations to be tested. The first results indicate that this approach might work and would help to collect additional yield above 5 kg/m2 in the third and fourth flush up to a predetermined limit of 10 kg\m2. It still requires some improvement and gradual implementation throughout the plant where the mushroom production and tests are carried out.

The development of this first concept has not been given up. These efforts to increase the compost water capacity and also using the possibility of soaking water placed in the bottom of the box lined with tightly foil have been undertaken.

08.2014 Casing

Colonized substrate that contains sufficient volumes of water and nutrient ingredients will not guarantee high yields if casing does not support the feeding process. Several performed tests followed by the implementation of the concept regarding controlled mushroom feeding provided data that lead into the conclusions describing conditions that are required so that casing will not decrease expected yields. It is obvious that the casing must have a uniform composition and structure, and should be evenly applied; not higher than 5 cm. The intense production requires medium or heavy casing. Light casing is not recommended due to its low water holding capacity. The specific requirements supporting the process of feeding besides water holding capacity are the following:

  1. Water shortage can not occur between casing application and end of the production process. Casing should be “shiny”, not matt. Water deficit causes mycelium drying and fruiting bodies, and in consequence a considerably decrease in the number of fruiting bodies particularly in the second and third flush. Water shortage worsens the quality of fruiting bodies, deprives their color and reduces yield by decreasing unitary weight: fruiting bodies are light. The mycelium should be white and alive on the casing surface during the entire production period. The addition of water into casing is easy, despite the growth stage of fruiting bodies irrigation will not worsen their quality as their nutritional requirements are fulfilled and their growth is controlled.
  2. Dry bubble disease (or brown spot) develops more intense on weakened and yellow mycelium.
  3. The casing must have a much higher salinity that is presently recommended and maintained, and it should be sustained at the same level throughout the entire period of cultivation. Appropriate salinity improves the quality of fruiting bodies and the yield by an increase of their mass and also pinning during flush is easier and more reproducible. Under these conditions the fruiting bodies are not exposed to short-term retention of their growth and respond better to activities aiming at the development of different generation stages. The salinity can easily be controlled, as there is a method, which allows taking direct measures from the casing. Effects of stable and higher salinity on mushroom yields in the third and fourth flush are expected.
  4. Stable calcium content. Research studies indicate a significant role of calcium in the feeding. The performed tests confirm the usefulness of calcium chloride in the feeding process. First, the pH should be stabilized as its decrease can enhance a risk of green mold occurrence on the casing surface in the third and following flushes. It is probably easier to fulfill calcium requirements of fruiting bodies if its source is provided in the casing. The transport time is shorter than that from the substrate. Besides, often application of calcium chloride induces a reaction with concrete and causes sealing concrete pores. This significantly reduces the risk of survival of spores of causal agent of dry bubble disease, as the concrete is the main source of infection within the cultivation hall.

Two-layer casing

So far the individual tests with the two-layer casing were performed. The collected results indicate that it might be a potential useful solution. An application of a hydrogel filled with liquid nutrients is a new idea that will be soon examined. This should create conditions supporting more sufficient colonization of the casing and better connection of mycelium with the substrate, and also shorten transport of components into fruiting bodies and primordia.

07.2014 Green molds and mushroom feeding

Green molds are the most important pathogens infesting substrate in the mushroom production. Their presence and the development of their colonies still present the potential cause of the most serious losses. I have been interested in this problem since early 2000. In Poland, the highest losses resulting from green molds infections occurred in the years 2002 – 2009. In 2009, I published the book “Green molds in mushroom production” (PWRiL) regarding this topic.

Presently, two genera of fungi, which are considered the green molds, are described as the main causes of losses in mushroom production. The highest losses result from infections by the genus Trichoderma, particularly by Trichoderma aggressivum. The recent data indicate potential serious threats from other pathogen Penicillium hermansii (smoky mold) Hermans C., Houbraken J., Smokey Mould: the smoke screen lifts, Mushroom Business, 061 November 2013. Both these species (strains) share one feature i.e. they are considered the aggressive mushroom pathogens.

How can one characterize a current concept of losses caused by the green molds that develop in the compost and infect mushrooms?

This theory assumes the existence of a correlation between the presence of spores of pathogens such as Trichoderma aggressivum and other species of Trichoderma spp. with competitive behavior and the smoky mold (Penicillium hermansii) in the compost, and also the development of their colonies as the result of infections with spores or mycelium, and destabilizing the selectivity of compost. This hypothesis can also be illustrated in other words i.e. colony size might be larger if more spores of pathogens survive during the compost production process and the compost is less selective. The losses resulting from the primary infection are the most severe particularly if colony development occurs in the tunnel. Whereas the secondary infections that happen between the completion of compost phase II production and at spawning until applying casing cause much less losses. It means the early and severe infections while the compost is less selective results in higher losses.

Despite numerous scientific studies there are no satisfactory results that would help solve the problem regarding how to protect the compost against infections of mentioned above pathogens. This situation becomes more difficult as a current problem of losses caused by Trichoderma aggressivum disappears in itself and the smoky mold does not indicate an increasing threat. There is no information regarding new green mold infections. Personally I have seen the infection with smoky mold several times over 20 years of my consulting practice. For instance, in the past the smoky mold infections were observed occasionally and did not cause significant losses. They are not perceived in many countries with the mushroom production. Regarding this situation one can ask the question if this problem solved itself and forever? Will we experience new infections in the coming years? If the infections do occur, how do we prevent the losses? So far there is no satisfactory answer.

Preparations of the concept regarding development of mushroom production technology as controlled feeding and its implementation requires additional review of this issue. Solving the problem of yield losses caused by the green molds considers two potential possible approaches.

  1. The first approach would exclude using compost in the mushroom production that would eliminate primary infections. Instead of the compost it is recommended to apply a substrate within control of its microbiological environment; lack of primary infections and protection against secondary infections by the simultaneous introduction of mycelium and casing application.
  2. The second approach considers changes in a feeding process that would protect the mushrooms against secondary infections and minor primary infections. In this case the compost plays the secondary role in a mushroom feeding. Properly composed feeders create conditions for full control of microbial composition of compost during its recolonization after their addition into a substrate phase III. The mycelium will become so strong that it will not allow pathogens to develop and compete for nutrients. The nutrient competition and pathogen presence are a main cause of losses in mushroom production. This means necessity to provide a surplus of mushroom mycelium during the recolonization process and during feeding after the casing application that a minor primary infection will not occur, and in consequences secondary will not take place either at a stage of placing on the shelves. This is a significant advantage regarding dominance over nutrients and competitors that might be present in the compost. This proceeding should be efficient enough. This approach is based on two assumptions that are accepted as legitimate. Although the genus Trichoderma and Penicillium are the competing species and more opportunistic towards food source that the mushroom, they show different food preferences. They utilize protein better than the mushroom, suggesting that there should be lower protein content in mushroom feeding. The second approach assumes that these species are not aggressive and they become destructive only in certain environmental conditions, and this aggressiveness is transmitted into another environment via vegetative way. Aggressive behavior occurrence among competing species has already been reported and it is not very rare phenomenon. The question is what causes this aggressive behavior. The following factors might be the deciding elements: colony size of pathogen, disruption in compost selectivity and process of compost colonization by mycelium. What is the reason that aggressive species and aggressive behavior have been discussed? It results from the fact that I have never observed secondary infections with Trichoderma aggressivum in places that had prior infections. It confirms that secondary infections do not occur in production facilities with high hygiene procedures that include steaming after compost production and also in facilities with very low hygiene without steaming measures. These observations refer to hundreds of reported cases. In contrast the losses caused by dry bubble disease (or brown spot) show a clear correlation between hygiene practice and the level of colony development of this pathogen. Performed observations indicate that a diet based on high polysaccharidecontent results in very rigorous expansion of fungous in the compost and that inhibits Trichoderma and Penicillium infections that might take place during the placing of substrate phase III on shelves.

I am interested in both solutions.

However, the pathogens might colonize the supplements and cause significant losses in production if these supplements based of vegetable origin, such as ground corn, are improperly prepared and stored.

A separate aspect is a potential mushroom strain that would be resistant to the green mold present in the compost. In my opinion, it is difficult to count on such a solution mainly due to the difficulties of identification of genes that should be modified to obtain such a resistance. Besides, finding these genes is one problem and another one is an implementation of genetically modified mushrooms into production and acceptance among producers. Presently the resistance can only be achieved in the genetic modified material and that also requires funds and executor. The current lack of real threat to mushroom production yield makes this issue of little interest among mushroomproducers.

06.2014 Water in compost and feeding

Water availability in compost should go through a review due to the implementation and development of the controlled mushroom feeding concept. The amount of available water must be significantly higher than in mushroom production that provides yields in range of 30-32 kg/m2 in three flushes.

All things considered, an important factor for good production appears to be water availability in compost that is reffered to as active water or built into compost water. Currently the active water plays a significant role primarily in the compost production phase. Stored water; built into compost water source is not sufficient to achieve high yields of very high quality mushrooms. Water shortage increases when thermal effect occurs in the compost. High temperature and necessity of intense cooling decrease the amount of water availability during the feeding process.

Compost moisture content during its production phase III cannot be increased above 67-69% due to the risk of incorrect course of production process. Water excess, particularly not built into compost during phase I causes disturbances in a balance of oxygen and proper course of the phase called hot composting. It can result in developing anaerobic environment. In turn in the wet compost phase II it is difficult to control a required compost structure during stage of overgrowth in tunnels or yielding spaces such as shelves, boxes, blocks. The compost with long period of cultivation creates the most difficulties. This favors the process of rotting.

High yields require absolutely much higher amounts of water availability for mycelium rather than currently used after placing a casing layer. This can be achieved in a correctly prepared compost, particularly if straw is loose and pliable with good structure and without the presence of competing and pathogenic organisms. These high water amounts are used in feeder enzymatic degradation and transferred into mycelium from substrate. The transfer of water into mycelium protects compost from rotting and overheating. Water shortage causes dryness of the compost.

The time period during which water is added is relatively short, less than 3 days after the recolonization and achieved compost temperature min 23oC with a trend of increase. The process of adding water should be performed after blocking air availability; placing casing. Water dosage should be determined in relation to the expected yield based on the rule 2 l/m2 and introduced feeder dosage. Presently, feeder dosage has been established for processed corn grain. The schedule of adding water must be established individually for each compost. It needs to include both its quality and quantity, and dosage and type of feeder. One can not forget that the added feeder absorbs water equivalent to its wage.

Lack of a balanced feeder dosage associated with deficiency of water availability will negatively affect the mushroom production. It will result in yield decrease and worsen its quality more than without a feeder.

All tests and cultivation are carried out on a substrate made of straw and chicken manure without horse manure.