Michael Davis
Overlay is a term used in mushroom cultivation to describe a condition in which the mycelium, or vegetative part of a mushroom, covers the casing surface. This is often the result of prolonged exposure to high temperatures, carbon dioxide levels, and humidity during growth. Overlay can cause mushrooms to grow improperly or not at all, and it can negatively impact yield. It is particularly detrimental to mushroom species that require a casing layer, such as Agaricus. While overlay can be broken up by scratching the surface, it is best avoided by initiating pinning at the appropriate time and maintaining optimal growth conditions.
| Characteristics | Values |
|---|---|
| Definition | Overlay is a term that refers to the condition that occurs when mycelium has been allowed to completely cover the casing surface. |
| Cause | Overlay is caused by prolonged vegetative growth temperatures, high CO2 levels, and excessive humidity. |
| Appearance | Overlay is often bright white and has a dense mass of mycelium growth. |
| Impact | Mushrooms will not grow on areas covered with overlay. It also interferes with watering as overlay becomes unreceptive to water. |
| Prevention | Overlay can be prevented by initiating pinning at the proper time and maintaining suitable temperatures and CO2 levels. |
| Treatment | Although overlay cannot be cured, it can be managed by scratching the surface with a sterilized tool to till the hardened casing and allow for new colonization. |
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What You'll Learn
Overlay is a dense mycelial growth
Overlay is a condition that occurs when mycelium has been allowed to completely cover the casing surface. It is often referred to as a dense mycelial growth. This condition is caused by several factors, including prolonged vegetative growth temperatures, high carbon dioxide levels, and excessive humidity. When a casing layer shows signs of overlay, it begins to shrink and pull away from the sides of the container. It becomes unreceptive to water, leading to the formation of puddles on the surface after misting.
The presence of overlay negatively impacts the growth of mushrooms. While a few mushrooms may still fully mature, most of the pinheads will abort. Overlay can be identified by its bright white appearance, resulting from the matted and impenetrable state of the mycelia. This condition renders the casing layer ineffective, as it can no longer serve its primary functions and essentially becomes a second layer of non-nutritious substrate.
To address overlay, it is important to initiate pinning at the appropriate time and avoid the conditions that contribute to its formation. While overlay cannot be cured, as the top layer of mycelia is dead, scratching the surface with a sterilized tool can help. This process breaks up the hardened casing, allowing for new colonization and the potential for mushroom growth. However, it is important to refrain from touching the exposed substrate with your hands to prevent contamination.
The impact of overlay varies across different species of mushrooms. For instance, Psilocybe cubensis can still grow reasonably well from uncased substrates, making it less susceptible to the negative effects of overlay. In contrast, species like Agaricus, which require a casing layer, are more negatively affected by overlay, experiencing a more significant reduction in pinset and yield.
In summary, overlay is a dense mycelial growth that covers the casing surface, impeding the formation of pinheads and the growth of mushrooms. It is caused by specific environmental conditions and can be managed through interventions like scratching the surface to enable new colonization. The presence of overlay highlights the delicate balance required in mushroom cultivation to maintain optimal growing conditions and minimize disruptions to the growth cycle.
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Overlay is caused by high CO2 levels, prolonged vegetative growth temperatures, and excessive humidity
Overlay is a condition that occurs when mycelium completely covers the casing surface. It is identified by its bright white colour and matted texture. Overlay is caused by high CO2 levels, prolonged vegetative growth temperatures, and excessive humidity.
High carbon dioxide levels in the growing room can be caused by a crowded microclimate around the mushrooms, preventing CO2 from escaping. This can be exacerbated by water stress or a virus, leading to premature growth and the characteristic long stalks of mushrooms affected by overlay.
Prolonged vegetative growth temperatures, combined with high CO2 levels, create an ideal environment for mycelium to thrive and spread over the casing. This continued vegetative growth results in a dense mass of mycelium that seals the casing, preventing water penetration and disrupting pinhead formation.
Excessive humidity in the growing environment can also contribute to overlay. When the casing layer is overwatered, the excess moisture provides the mycelium with the ideal conditions to proliferate and form a dense, matted layer. This layer becomes impenetrable to water, and puddles may form on the surface after misting.
The presence of overlay negatively impacts the pinset and yield of mushrooms. It renders the casing layer non-functional, as it can no longer serve its primary purposes. This disruption leads to the abortion of most pinheads, and only a few mushrooms fully mature.
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Overlay can be identified by its bright white colour
Overlay is a term used in mushroom cultivation to describe a condition that can occur when mycelium has been allowed to completely cover the casing surface. It is identified by its bright white colour and can be caused by prolonged vegetative growth temperatures, high carbon dioxide levels, and excessive humidity. Overlay can also result from failure to initiate pinning early enough or not flushing hard enough.
The bright white colour of overlay is due to the matting of the fine strands of mycelia, which have died and become hard. This layer of dead cells is impenetrable, and mushrooms will not grow from it. The mycelia layer is literally dead, and while it cannot be cured, it can be helped by "scratching" it with a sterilised tool to till the hardened casing and allow for new colonisation.
It is important to note that scratching the casing layer is not advisable as it opens up another route for contamination. Additionally, dealing with overlay can impact production efficiency as the mycelia have to recover and re-colonise the casing layer, which can set back the process by at least a week.
The effect of overlay on the pinset and yield varies depending on the mushroom species. For example, Psilocybe cubensis can still grow well from uncased substrates, so a functioning casing layer is not as crucial for this species. However, for mushrooms that require a casing layer, such as Agaricus species, the impact of overlay on the pinset and yield can be much more negative.
Identifying overlay by its bright white colour is crucial in mushroom cultivation to address the issue promptly and minimise any negative impacts on the pinset and yield. By understanding the causes of overlay and its visual appearance, growers can implement preventative measures and appropriate interventions to ensure healthy mushroom growth.
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Overlay prevents mushroom growth
Overlay is a term used in mushroom cultivation to describe a condition that can occur when mycelium is allowed to completely cover the casing surface. It is often bright white and impenetrable. Overlay can be caused by a variety of factors, including prolonged vegetative growth temperatures, high carbon dioxide levels, and excessive humidity.
When overlay occurs, the mycelium layer becomes matted and hard, forming a dense, dead layer of cells on the casing surface. This layer is unreceptive to water, and puddles may form on the surface after misting. The casing layer loses its functionality and essentially becomes a second layer of non-nutritious substrate. As a result, mushrooms are unable to grow from this section as the mycelium layer is dead and cannot be penetrated from below.
The effect of overlay on mushroom growth varies depending on the species. For example, Psilocybe cubensis can still grow well from uncased substrates, so overlay is not as detrimental to this species. However, for mushrooms that require a casing layer, such as Agaricus species, overlay can have a more negative impact on the pinset and yield.
To avoid overlay, it is important to initiate pinning at the proper time and maintain suitable environmental conditions. While overlay cannot be cured, as the top layer of mycelium is dead, it is possible to scratch the surface using a fork, knife, or another tool to till the hardened casing and allow for new colonization. However, it is generally not advisable to touch the casing layer, as it may introduce contamination. Additionally, scratching the casing sets back the growth process as the mycelium needs to recover and re-colonize the casing layer.
By understanding the causes and effects of overlay, mushroom growers can implement preventive measures and mitigate its impact on mushroom growth. Proper timing and environmental control are crucial to avoiding overlay and promoting healthy mushroom development.
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Overlay can be avoided by initiating pinning at the right time
Overlay is a condition that occurs when mycelium has been allowed to completely cover the casing surface. It is caused by a variety of factors, including prolonged vegetative growth temperatures, high carbon dioxide levels, and excessive humidity. When overlay occurs, the casing layer loses its functionality and becomes a second layer of non-nutritious substrate. This leads to reduced pinhead formation and interferes with watering as the mycelium seals the casing, preventing water penetration.
To avoid overlay, it is crucial to initiate pinning at the right time. Pinning refers to the formation of pinheads, which are the early stages of mushroom development. By starting pinning early enough, growers can prevent the mycelium from overly colonizing the casing layer and causing overlay. This involves creating the right environmental conditions, such as maintaining appropriate temperatures and carbon dioxide levels, to encourage pinning and subsequent mushroom growth.
Additionally, proper flushing techniques are essential. Flushing involves reducing carbon dioxide levels and lowering temperatures to create optimal conditions for mushroom growth. If flushing is not performed effectively, it can contribute to the development of overlay. Therefore, ensuring that temperatures and carbon dioxide levels are not left "too high" for "too long" is crucial in preventing overlay.
The presence of stroma, a genetic malfunction in spawn culture, can also impact the initiation of pinning. Stroma results in dense mycelium growth, which can interfere with pinning and mushroom development. By addressing stroma through proper spawn-making processes and transport methods, growers can reduce the risk of overlay.
Overall, by initiating pinning at the appropriate time, maintaining suitable environmental conditions, and addressing factors such as stroma and flushing techniques, growers can effectively avoid overlay and promote healthy mushroom development.
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Frequently asked questions
Overlay is a term used in mushroom cultivation to describe the condition that occurs when mycelium has been allowed to completely cover the casing surface.
Overlay is caused by prolonged vegetative growth temperatures, high CO2 levels, and excessive humidity.
Overlay is often bright white and matted, and it can form a dense, dead layer of cells on the casing surface.
Mushrooms will not grow on any parts covered by overlay. Overlay can also cause mushrooms to grow long stalks that open up small.
Overlay cannot be cured since the top layer of mycelium is dead. However, it can be helped by scratching it with a sterilized tool to till the hardened casing and allow for new colonization.
