Imagine the third picking day of a first flush. In the morning the pickers are picking a beautiful mushroom. Around noon the mushrooms are starting to lose colour and 3 hours later they start growing like mad. Stems are stretching and caps are getting soft.

Does that sound familiar?
In that case look at the casing. If you start checking the casing it is very well possible that it is getting warmer. The differential between ambient temperature and casing temperature is gone. This means that the evaporation has almost or completely stopped. In other words: the casing soil is too dry.

Watering at that moment is too late. If water is applied at this moment the mushrooms will lose the colour completely and bacterial blotch is the next problem.
To solve that problem the grower has to look at the next room where the next flush is coming. In the last days of outgrow water can be given on mushrooms that have the size between a pea and a cherry. Generally, that is about 3 days before the start of the harvest of the first flush. The amount of water can be around 2 litres per m².
Just one watering can be enough to solve this problem.

But only if the rest of the circumstances are okay. A good open and heavy casing soil which can hold that water.
And good selective picking so the outgrow of the flush during the harvest is more gradual and not explosive.
It is possible to detect the moment when the casing is drying out by using an infrared thermometer. If the casing soil temperature is getting up, the casing dries out. The right watering moment is just before that point.

These three principles are the base of disease control on a mushroom farm. To my opinion there is no farm that has not a spot of disease somewhere.
But depending on what is done it will develop into a serious problem or it will stay a hidden time bomb.
If a problem is discovered it is of crucial importance that is recognised. To make sure that will happen training of people on the farm and especially pickers is needed. They are your eyes on the farm.
They need to know the most common diseases and especially in a young stage. Many places of dry bubble are not recognised and are only seen if the disease is in an almost incurable stadium. The small wart on a mushroom or grey spot is often missed.
The same goes for insects. Many growers do not know the difference between a phorid and a sciarid. Although the damage pattern is totally different, so Is the threshold where it really starts costing production. Also the cure is completely different.
Example: growers use diflubenzuron against phorids.
It is only active against sciarids.
If the disease is recognised then it should be isolated. It can be covered on the spot but the most important is to simply keep all doors closed. Check filters and door seals. If a room is infected, make sure the infection is contained in that one room and does not spread on the farm.
After the isolation the disease can be treated. If the spot is detected in an early stage one can do with just a sport treatment. If it is more the whole room should be taken on.
But too often the infection spreads and the whole farm must be treated. Generally room treatment for a full cycle with an overlap of two or three rooms to break the lifecycle of the disease.

So, just a test:
Look at the photo and spot the phorid. Or is it a sciarid?

A sentence often heard in logistical companies but even more nowadays in mushroom growing.
Due to short schedules, labour management and supermarket requirements timing in the growing of mushrooms is essential.

If mushrooms are not in time one can loose part of a flush. The compost for the next room is ordered. Supermarkets need the mushrooms on the shelf on a set time and for the organisation of the picking force a strict timing is needed. Even if it is just to stay away from picking in the weekends to avoid high labour costs.

To ensure a right start of the first flush on the desired time many factors are involved.
The activity of the compost is one of them. An active compost or an inactive compost can easily make a difference of a few days in the start of the first flush. A corrective measure there can be supplementing. And for all the choice of supplement and the quantity. Especially in combination with the right type of casing soil this has great influence. No need to say that both compost and casing soil need to have a good stability. The combination of those two can be seen in the amount of caccing and the deepness of the casing layer.

Water on casing soil is the next determining factor. It is well known that water can stop the mycelium from growing. A factor that can be used to time flushes.
A very strong tool is the ruffling machine. By ruffling the grower can time flushes even more accurate. Generally ruffling is done between days 3 and 6 after casing the room. Later ruffling often also means a slower recovery because older mycelium has a slower re-start. Ruffling is done a lot by farms who have very strong time requirements by the supermarkets. A negative aspect of the ruffling can be that the staggering of the flushes is more difficult. But this can be overcome by changes in the climate setpoints during fructification.

So just looking at timing of crops, the grower has many options. Unfortunately this also means enough options to make mistakes but isn’t this what makes mushroom growing interesting?

Henk van Gerwen

Too often there are problems with second flushes. The first flush is rather normal but not extra-ordinary. The problem starts showing on the third harvesting day of that first flush by loss of quality and second flushes do not come back the way they should.
If the casing soil of those rooms is examined closely then it will appear that whatever water is given, it is still very dry. All water given after the first flush seems to be gone before the flush has even started.
Most of the times there is too much mycelium in that casing soil. A problem what was already there before the start of the first flush but really shows in the second.
At that moment the problem cannot be solved anymore. One has to look for solutions before even the fructification has started.
Solutions lay in the choice of casing soil, the amount of water on that casing soil during incubation, the way of watering and in the climate control during casing soil incubation.

Too much mycelium results in too fine strands of mycelium and therefore a lack of water transport to the mushrooms. Mycelium dries out very fast and too much mycelium forms a crust together with the casing soil. What is needed is a thick, white type of mycelium. Only this can guarantee strong, heavy and white mushrooms. Especially in second flushes.

Henk van Gerwen