IN scientific papers and in articles for The Mushroom People (M.P. for short) I have frequently used the word Agaricus, being short for Agaricus bisporus, the latin, taxonomic name for the mushroom species that is usually grown in Ireland.
Consequently, I was surprised to read on the label of a ‘new’ brand of disinfectant the word Agaricus, along with Trichoderma and Verticillium etc., grouped as major pathogens that the product would kill!
Of course mushroom mycelium in the wrong place could be regarded as a pathogen if, for example, it contained a mushroom virus and was growing in the wood of a compost tray. It could thus put at risk newly-spawned compost.
However, a previous experience suggests this product had not been tested against the organisms it claimed on the label to kill. That is unless the product was an exact copy of one that had been tested. I ended up wondering if I caused the confusion, using the word Agaricus in my articles?
I remember with some embarrassment reading that I had endorsed another ‘new’ disinfectant, aimed at Trichoderma. This had been launched by a well known Irish sports personality. Far from it, I had just been the uncomfortable witness at a so-called demonstration. This, I felt, was more like an incantation than a scientific test! However, copious amounts of booze was flowing and most of the audience was impressed. Buckets are still landing with considerable force.
I wrote an M.P. article on overlay using a similar title. In it I had agreed with Carl Bozicek that at least one cause of overlay could involve wet casing. Particularly if it filled a ‘deep pool’ contained in a dent made by the casing bucket landing hard on the surface of a poorly compacted bag.
I saw a good example recently. Casing had arrived wetter than normal. It had been difficult to apply because wet casing sticks to the buckets. These had been slammed down to help empty them. Casing was often 10cm (4 inches) deep in the centre of the bag, tapering to 5cm at the edges. Where the casing was deep it was anaerobic and smelled of hydrogen sulphide. The mycelium had grown up from the edges and arched over the centre.
In about one-third of bags it had not quite made it and these had black centres. The grower had narrowly avoided overlay (or over run) on the remaining bags by somewhat delaying the break. However, realising the danger, he had aired early and gone for a long slow break. Yield was down but mushrooms were well spaced and of good quality. One man’s meat is another man’s poison.
Casing manufacturers provide drier casing for bag growers than for shelf growers. The latter like a wet, sticky casing as they have machinery for spreading and ruffling it. Applying wet casing restricts the amount of mycelium coming up through it, thereby helping to better space the crop and improve quality. Bag growers are influenced by the men who do the hard work of applying the casing and go for one that comes out of a bucket easily and requires only a flick or two for levelling. However, this type of casing ends up with a multitude of cracks and airways that tend to encourage excess mycelium growth into it.
At this time of year, especially after prolonged rain, casing is occasionally likely to be over-wet for use by bag growers. If this occurs, could some innovation result in a good crop of better quality mushrooms? Small holes in the bottom of the casing bucket may help break the vacuum, so it releases its contents easier. Or, what about a ‘casing scoop’ — two scoopfuls per bag? I intend to try some experiments. Watch this space! A rose by any other name would smell as sweet.
I’ve never fully understood that quotation, so maybe it’s an appropriate heading. Descriptive terms for casing sometimes appear to be only understood by their user! Even a simple term ike ‘heavy’ could be ambiguous. Does this mean a casing that weighs heavy per litre or does it mean heavy to work with, sticky and requiring a lot of effort to get it out of a casing bucket? Or does it mean there are less air spaces in a bucketful of such casing — so the bucket feels heavier?
I have spent several months working part-time for a casing manufacturer, setting up a small laboratory and trying to develop some rapid, user-friendly, tests. I have found the ‘standard’ tests slow and sometimes hard to interpret. My new experience makes me want to discuss with growers what they like and dislike about certain casings and maybe design a questionnaire.
However, terminology is going to be a problem. It is said that Eskimos have a dozen or more words to describe different types of snow. I wonder if mushroom growers need a similarly enhanced vocabulary to describe different types of casing!
In a bucket of casing, some of the peat could be 6000 years old, some 20 years old. The younger the peat the browner and less broken down it is. If it contains a high proportion of sphagnum moss it will also have a high content of trapped air, consequently the peat will weigh less than 1000g per litre, even when saturated with water. The many airways in such peat could allow too much mycelium to get up through it. Peat with a high proportion of undecomposed sphagnum is usually mixed with black peat to reduce the number of potential airways.
The first casing vocabulary problem arises because there are many types of black peat. Some derive from very broken down, degraded sphagnum and have very little structure. Others have quite a high sedge or grass content. These plants provide long fibres that give the casing ‘structure’ even when wet.
Black peat can also have a high proportion of birch tree leaf, twig and root remains, along with water loving plants like bull rushes. Such a peat could weight as much as 1030 grms per litre. Peat structure also depends greatly on the volume of water it contains and the amount of physical stirring it has received. If black, ‘birch tree’ peat was ‘stirred’ relatively dry (with a moisture volume of say less than 87%) it could break into particles and end up looking like black gravel, with an enormous number of airways. The same peat with a water content of over 90% by volume could end up as a slurry, with no apparent structure and later ‘setting’ extremely solidly after drying out somewhat.
The casing manufacturer’s ‘art’ lies in blending different peat types, adjusting moisture content, neutralising the humic acids in the peat using an appropriate source of calcium carbonate and adding extra of this or other weight increasing ingredient, as required.
A casing that has a weight of say 1060 grms per litre, fully compressed, will be middling heavy. If it also has a high water content, to make it more ‘fluid’, like thick mud, it will settle on the compost, provide relatively few air ways and produce relatively few, large, high quality mushrooms. The mystery ingredient, sugar beet lime (SBL).
It is commonly observed that SBL increases quality yet SBL is almost as variable as peat itself. It ranges from grey and clay-like to brown and powdery.
Part of this is moisture content and how it has been aged and for how long. Furthermore it may or may not have been pasteurised. This may be done to make sure it is free of Salmonella. The Salmonella problem now appears to have been resolved. It has had several useful long-term outcomes. For example, it is no longer permitted to send spawn run compost to casing manufacturers to make CACing out of it. This must have greatly reduced the risk of casing spreading Trichoderma and other diseases. Standards have also been substantially raised by manufacturers but his has increased their costs.
There is not much documentary evidence as to why SBL increases mushroom quality. It is made up of very fine particles of calcium carbonate, which being so small, react quickly and easily with peat’s humic acids. Yet SBL is often so sticky it goes into the casing in poorly distributed lumps. SBL is said to decrease blotch and also increase yield. Some pioneering work by Ralf Noble employed very high proportions of SBL, but these were added to brown sphagnum peat.
The latter has such a low weight per litre that it could have benefited greatly by the relatively very high weight per litre of SBL. However, where SBL is expensive, its weight increasing role has sometimes been successfully replaced by using chalk chippings or rock dust from coal mining.
With black-peat casing, especially if already relatively ‘heavy’, SBL may not be needed in nearly such high proportions as used originally with brown peat.
Low temperature mushroom growing.
Some small experiments, to try and find out more about the benefits of SBL, were allowed to proceed at a mere 10ºC. Mushrooms still form and can be of good quality, provided the humidity is not allowed to fall too low. The interesting point is that everything takes about three times as long, as at normal temperatures. This would usually be a big disadvantage.
However, at Christmas, slowing the rate of production could give time for the turkey to settle! Changes in growing temperature should be made gradually. Otherwise there is a risk of humidity changes causing scaling.
