One of the most seen disease in mushroom farms is the dry bubble, caused by the fungus Verticillium fungicola. Its easy to get an infection in the farm and because the disease is very infectious it can spread quickly through the whole farm. Especially in big farms, where many pickers are working, the dry bubble will spread very fast and can cause a lot of damage and be that bad that 3rd breaks may be lost. Pickers should be getting all the information about the dry bubbles so they can detect the infection in an early stage.

2021 Blog week 7 Article dry bubble

A dry bubble in a 2nd break.

Dry bubble is generally caused by spores around the farms in windy, dusty conditions. On filling days when its windy outside with dust in the air its very well possible to get the dry bubbles into the farm. When they are spotted before he 1st break, the infection came in at filling. Once inside it’s a matter of time before the spores are everywhere if not handled well. Hygiene on the farm should be checked and especially have a good look at all the materials that are used for your mushroom waste like stem bins. Spores of bubbles will be present there if not cleaned well and can be spread if materials are getting moved between rooms. Also pickers are a concern for spreading the infection. Spores are sticky so everything that gets touched after touching a bubble can get infected, be aware!!!, it can go rapidly.

Removing the bubbles is off course also very important. When the pickers don’t recognize a bubble and are picking mushrooms while touching dry bubbles it will be always be hard to control the infection rate. Educate them well and spread around as much information as you have to inform pickers about the diastase and the big risk it has on the results of the farm. Let them, or the picking lead, report the infection so a special crew can handle it the right way.

When the pickers recognize the bubbles, the next step is removing the infection as soon as possible. Makes sure when you remove the bubble you don’t spread the spores what will results in more bubbles within 4 to 5 days. Use a wet tissue to cover infected spots too avoid the spread and remove all the spot including the casing soil, using a plastic bag. Close the bag immediately after you have the bubble and surrounded casing soil inside and remove the bag from the farm as soon as possible. You can also leave it in the affected room and remove it after cook-out. After removing it use salt or ammonia to cover the infected area and inspect the area every day to see if the infection is spreading.

It all comes down to a good hygiene, organization and education. Infection can occur suddenly but if threated the right way can also be stopped rapidly. Organize it well so that infections get removed before rooms get picked or watered, those are moments when spores will spread. If everybody recognizes the disease and knows what to do and handles right, bigger problems can be avoided. Hygiene is key, not only for dry bubbles, and should never be underestimated.

Erik de Groot
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Chicken manure

Jan 26, 2021

Chicken manure is an important raw material in mushroom compost and for the composter as it is the biggest source of nitrogen. It is therefore vital to keep the quality as consistent and as high as possible. However, the quality of chicken manure is unimportant for the farmer, for him it is a waste product. So make sure you always pay attention to the following points yourself.

Achieve the best quality with: - a nitrogen content (N) of 3.5 to 4%. The higher, the better; - a moisture content between 20 and 50%. The majority of composters work with dry chicken manure. The most suitable type is manure from broilers. This contains a higher percentage of actual manure compared to the rest of the constituents such as sawdust.

Regular supplier
One of the main aims of composting is to create homogenous compost: ensuring that you always supply growers with the same quality of spawnable or incubated compost. This process starts with selecting your suppliers, including the ones who provide you with chicken manure. Always work with the same chicken farmer, who keeps his birds in the same way. If you do not have a regular supplier, then you will have to compensate for the differences in the chicken manure.

Analysis is essential
Even if you do use a regular supplier, analysing the nitrogen and moisture content in the manure remains essential, even though the results of the analysis are usually the same readings. If the birds are sent to slaughter earlier or later than usual, there will be a direct influence on the nitrogen content. You won't see it visibly in the manure, but it will appear in the analysis. Using the wrong recipe to blend the compost has immediate and far-reaching consequences for your mushroom production. You won't be the first person to have two weeks of bad production….

Distribute well
Distributing the chicken manure over straw can only be done well once. The blending done afterwards will not compensate for any bad initial mixing. Every single blade of straw must come into contact with the manure. You must avoid any large lumps of chicken manure ending up in the compost.

The last month several growers had problems with a too heavy casing soil. It is normal for this time of the year for casing soil to be heavier because of rainfall on the peat fields. It takes a few weeks for the casing companies to sort this out and in the mean time the grower has to deal with this. A normal situation for this period. Complaining is not the way to deal with this but inter acting is possible.

The first thing to do is to recognize that the casing ís heavy. This can only be observed if good attention is given to the filling of the room. Always talk to the truck driver about compost and casing and you already know a lot. They know exactly what material they carry. If they say it is a heavy load and if water is coming out the first thing to do is to adjust the filling machine. Heavy casing soil packs more so it has to be opened up. The caccing spinner on the combine filling machine plays a big role in this. It has to pick up the compost and mix it well into the casing. Cac a bit more than normal if casing soil is heavy. The next step is to make the mixing spinner turn a bit slower. Too intensive mixing will destroy the structure and cause big problems in outgrow of the pins later on. The pressing roll should be adjusted that way that it does not close the holes in the casing. If you look at the roller from the side of the shelf, a little bit of light should be visible between roller and casing.

Then be careful with water on the first day. Make sure the caccing material starts growing. This can be seen by the attachment of the compost to the casing. Do not wait however till you really see the mycelium. Because then the time for watering can be too short. And mycelium will overgrow the casing. The normal amount of water can be given minus a few litres. (the water on day one). It is a good thing if watering gifts can be split into small doses. 1 litre at a time with intervals of at least 1 hour. Only on the first watering day (probably day 2 after filling) bigger gifts are possible.

The next thing that might happen is that the mycelium has difficulties growing to the surface. Remember, a heavy casing soil needs help to release water and CO2 so always make sure that fresh air is given to the room. A minimum of 5% fresh air most of the times helps a lot. If the mycelium has reached the surface generally the fructification is normal. The only difference is from day 7 to day 10 of the fructification. From that day 7, the pins might stagger in outgrow. At that moment again fresh air is needed to keep the evaporation going. A minimum of 5% might not be enough anymore. If you see pins but they do not grow out you have a few possibilities.
A drop of water as a shock. This means 0,5 litre of water and mild drying with heating and fresh air. Fan can be set up to 5% higher in speed.

Or you can drop the CO2 to about 1000 ppm for a day. But make sure that RH stays over 88% in this case.Overall the growing later on will be on a bit lower CO2 than normal to keep evaporation going. Watering as normal. The biggest mistake made is to keep rooms like this too dry. Be aware that the room might develop less pins than normal. Let them grow out and pay special attention to the picking. This way these rooms do not have to be any worse. On the contrary, often they are better (in a financial way) than normal.

Recipe for a new year, keep the buttons up!

March 2020. Everything looks good and I have got my pocket full of tickets. Flights all over Europe and many visits to make.
But a week later everything looked different and still does.
Corona is sweeping over the world and people do not know what to do. Traveling has come to a stand still and most of the consulting is done over the phone.
But does it have good sides too?
Fortunately, so. It is a proven fact that corona has less chance to infect you if you are in a good state of mind in a fit body. Or at least the symptoms are less severe.
For most people in this modern world that is a bit of a problem. A great deal of mankind has a problem with being too heavy and is suffering from obesitas.
And just this morning I heard that loosing 5% of bodyweight (if you are too heavy) means already a big boost to your immune system.
So, go outside, exercise and eat good food.
And it is a proven fact that mushrooms exactly fit into that diet.
Mushrooms are low in fat, rich in vitamins (vitamin B and D even more in brown Agaricus)and they are loaded with complex carbo hydrates.
A good reason to eat mushrooms and use it as advertising. Countries as Spain and Hungary are already doing this on a large scale and I am sure many other countries do the same.
But it can be a lot more. If I just look at Holland, the consumption is still very low and that can only be changed if we as growers tell about the health aspects of our product.
And of course, the taste is good.
To give an example I would like to share a recipe with you.

Mushroom Gougère. (serves 6)
Melt 75 grams of butter in a pot.
Add 2,25 dl of water and bring to the boil.
Add 100 grams of wholemeal flower at once and mix well.
Mix till the dough lets go of the side of the pot.
Let cool a bit and then mix in 3 eggs, one by one.
If the dough is smooth, mix in 75 grams of grated cheddar cheese.
Put the dough into an oven dish. Leave the middle open. Put the dough only on the outside rim.

Then put some oil in a skillet and fry 2 chopped onions.
Add 2 cloves of chopped garlic and I kilo of sliced mushrooms.
Add one spoon of wholemeal flower and 2 dl of vegetable broth.
Bring to the boil for 3 minutes till the mix thickens.
Then add 200 grams of chopped walnuts and 2 spoons of chopped parsley.
Ad pepper and salt to your liking.
Put this mix in the middle of the dough in the oven dish
Cook this in the oven at 200° for 40 to 45 minutes.

If you share this recipe with your clients you might sell a lot more mushrooms and create a healthy and good world.

Best wishes for 2021 and stay healthy.

Henk van Gerwen


I am writing this blog on November 2. 2020.
It is the warmest November day ever. The outside temperature today will hit 20° C. Normally this time of the year in Europe growing is fairly easy. Older growers always say: just open the doors and let the outside climate do the job. This year and probably oncoming years the situation is different. It starts with arable crops being harvested later than normal. The potatoes are still being harvested and the corn is only gone this week. Meaning that there was a lot of dust and organic material flying around. Especially since many farms are situated in rural areas. All this organic matter being airborne has caused a big problem with Mycogone and verticillium. But another and maybe even bigger problem is that the insects are still there. It is known that phorids stop flying around 5° C and sciarids even fly till it starts freezing. And that situation seems to be far away. And that is why I see at many farms that the infection with sciarids was almost gone but is returning (rapidly) again. Because their hiding place in the corn is gone. Just at the moment when many farms are scaling down on fly control. The combination of these two factors, the insects and the dust causing bubble, is a dangerous one which may last for another month or so. What to do about it? Trying to kill the verticillium or Mycogone is the first thing growers do but if the vector (insects) to carry the spores is still there the problem stays. That is why I always try to aim at the insects first. In this case practically always a problem with mosquitos or sciaridae. Often chemicals are chosen and many times a combination of a short term chemical by fogging and a long term chemical as a drench on the casing soil. But lately I see very good results (as good as the chemical treatment) with the biological control with nematodes as a drench on the casing. In price there is not much difference but in application it does make a difference. It is not dangerous for the person who applies it and it is not dangerous for the environment. On the other hand it is noticed that many supermarkets want a clean, read: chemical free, product. And nematodes are not regarded to be dangerous. Even more, farms use it as advertising for their product. It is the same as with my own business “Akkie’s Tuin”. An apiary and orchard. We do not use chemicals, only biological control and we use that as a selling point. We notice that we can get higher prices for our products by working organic. The only thing is that the customer needs to know what you do. With the product goes the story about what you do. So if you have an insect problem at the moment take this into consideration. A few remarks on the use of nematodes. Make sure they are delivered fresh onto the farm and put them into the cold store right away. Overheated nematodes will die. When using them, you need sciarids on the farm. The nematodes feed on the larvae of the mosquito and if there is no food they will die. The manual about using the nematodes often says that they have to be applied directly after casing the compost. I however have better experience in the so called split application. So not the 2 million nematodes per m² directly after casing but 1 million on the casing day and the other 1 million 4 to 7 days later. I prefer 2 days before the start of the recovery period as the last day of application. So practically this means the second application on day 4 after casing. If you apply it a day before recovery you knock back the mycelium too much.

But whatever you do, do it now. If you think that frost will stay away for a while and you see some sciarids flying around, waiting is not an option. Especially is you also have a bubble problem. And the difference between sciarids and phorids is fairly big. As a reminder: Phorids have a nasty smell if you smash them under your finger, a sciarid has no smell. Phorids are fast moving. They walk fast. A sciarid has the tendency to just sit. Phorids are a lot smaller and the antennae are practically not visible while the sciarid has large visible antennae.

Climate control

Oct 12, 2020

A good climate control is of course vital for every mushroom grower even more if you want to stand out with the quality of the mushrooms. One of the most asked question I get as consultant is: How can we get better quality and how can we keep the quality of the mushrooms good until the end of the flush? Now, of course the quality at the end of the flushes will always be less than at the start, no illusions there. But improvements are always possible and most of that you can get from an ideal climate.

Before we had more advanced climate installations with more options, we always controlled the rooms on Air temperature, Relative humidity and CO2. However, with the new systems coming on the market there is a lot more to learn than we think and controlling rooms, especially in harvest stage, on moisture deficit, inlet moisture control and even measuring systems for evaporation are used.
To understand the difference between all the systems you need to know exactly what the Mollier Diagram stands for and if you manage to run the system well you will see advantages, especially in quality of the mushrooms. The Mollier Diagram is crucial in mushroom growing and climate computers make the changes in the room based on that Diagram with the Absolute humidity (AH) as the biggest factor. Let’s me explain a little bit more about of those controls, the moisture deficit.

As we are changing air temperatures in the flushes you will see in the Mollier Diagram that that will create differences in evaporation as we change the temperature but leave the RH the same, with other words, we change the AH. By controlling on moisture deficit we will maintain a constant evaporation, what will benefit the quality of the mushrooms, no matter what the temperature differences are. The computer will calculate the right RH for the current air temperature, to keep the same evaporation in the growing room.

Moisture deficit is the difference between the current absolute humidity in the room and the maximum possible absolute humidity at the same air temperature. Once this value is constant the evaporation capacity of the air is also constant.

To use this in a practical situation of course first of all you need a climate control computer that supports the moisture deficit system and change it from RH to moisture deficit control, in the computer that will be named as Absolut humidity control. Ideally this is linked with humidity control of the inlet air to get the best benefit. The mushrooms will have a constant evaporation and that will benefit the quality as changes in evaporation will disturb their growth. The mushrooms will get less water stems and go softer in a later stage what would give an extra picking days benefiting the yield as well as quality.

I recommend to change the computer 1 day before you start harvesting the flush from RH control to moisture deficit control. When you changed the control, set the AH in the computer so that the RH is at the same level as you normally run it in the flush. So if you normally run the flush on 17.5 degrees and 89% RH, keep the air temperature the same and set the AH so that he calculates the 89% RH as set point. Keep 0.2 difference between minimum and maximum AH. From that moment forward you let the computer calculate the right RH and change the air temperatures as you normally do, until the end of the flush. After the flush put the system back to RH control.

The only way to find out is try other controls to improve quality. Many option are out there and based on results on other farms worth trying. If you start and are seeing any improvement? Learn more and keep doing trials, good luck.

Erik de Groot
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