Trichoderma causes severe damage. Causes include too high mycelium growth temperatures, water or condensation coming into contact with spawn and poor hygiene.
Well-incubated compost is less sensitive to infection
moulds such as trichoderma will be encouraged. At 28 degrees, trichoderma grows 10x faster than mushroom mycelium. At even higher temperatures the growth of mushroom mycelium starts to stagnate and even stop altogether. Trichoderma on the other hand will continue to flourish. Extra alertness is necessary in situations with a high filling weight, high outside temperatures and compost transported in vehicles without cooling facilities. Dry compost
Mushroom mycelium will not grow in dehydrated patches of compost which can occur in the lower compost layer in incubation tunnels, and in the upper layer if compost is incubated in trays. Other moulds, such as penicillium can still develop well under these conditions. Later in the cultivation process, when these moulds come into contact with water and supplements, they can cause a considerable temperature rise. Humidi- fying systems can go a long way to preventing dry layers of compost.
Dense, compact lumps
Mycelium cannot grow in compact, dense lumps, often caused by using recycled compost, old, poor quality straw or heavy horse manure – but plaster moulds love these conditions. This can cause huge problems, especially on phase II composting plants. Condensation During mycelium growth in blocks, condensation forms immediately underneath the plastic film. This conden- sation, combined with any grain spawn left on top of the compost, is often the first base camp for a trichoderma attack. Condensation cannot be avoided completely, but it can be managed by ensuring the film has enough perforations, opening the film in time, avoiding too wet compost and maintaining a tight temperature regime.
Mycelium growth days
Well-incubated compost has a self-defence mechanism against infection by other moulds. The longer the compost is allowed to incubate, the better the individual compost particles will be enveloped by mushroom mycelium, and the less sensitive the compost is. This is a more important factor for mycelium growth in tunnels than with mycelium incubating on blocks or beds. Mycelium suffers extensive mechanical damage when a tunnel is emptied, a lorry unloaded or the beds are filled. On poorly incubated compost the majority of the mycelium will be wiped off the compost particles, and many ‘open wounds’ occur. What the mycelium really needs is time to recover, but it is not given the chance as the casing soil is applied and the grower has already started watering. This creates a barrage of water, moulds and bacteria in the upper layer of compost, which is not always in a condition to put up any resistance. On well incubated compost, the mycelium is far better anchored in and on the straw particles and can cope better with this mechanical damage. In typical Dutch conditions, we have learned that compost incubated for 16-17 days is the most stable. If compost is incubated in blocks and in beds, the mycelium is not subjected to this mechanical damage, so a slightly shorter incubation time suffices.
We always speak of ‘ the number of days of mycelium growth’, but what we should actually refer to is the ‘intensity of mycelium growth’. The drop in pH from inoculation to incubation is often a better indicator in this case.
The following article in this series will discuss how growers should respond to coax the best performance from good quality compost.
MUSHROOM BUSINESS 37
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