On contamination:
Most people are worried about their ability to determine contamination in their grow.
So here is a little primer.
First, p. Cubensis mycelium is snow white, pure iridescent white in the absence of any color benieth it. I can occasionally be tinted blue and on rare occasions blue green - but this is only the very slightest of color and it is a result of bruising, AND that bruising color will usually only become noticeable later in the life of the mycelium.
the mycelium will tend to grow in a parallel fashion early on, it is very fine and straight.
View attachment 2548216
Notice in the picture that the mycelium does NOT look white, in the lower quadrant you will see a gun metal blue, this is the result of bruising as the mycelium becomes "aerial" rising from the mass, now note that you don't see pure white in the upper portions either, this is because the mycelium has not yet gained enough density to overcome the yellow brown color of the agar benieth. While we are at it, note the divisions between the colonies. Each geneticaly different colony will tend to avoid the other - this is why you will rarely if ever see a "multipoint" innoculation work as well as a monoculture. When you squirt hundreds or thousands of different cubensis spores into a jar you will get dozens of geneticaly different colonies each competing with the others. Two compatible colonies will eventually find each other as this mushroom is tetrapolar (having 4 spores emanating from each basidia (platform) which in this case grows on the gills of the mushroom. Each unmated colony are monokaryons - that is they do not have a full complement of genetics and cannot fruit. When two complementary monokaryons touch, they become dicharyotic and are then able to reproduce. The mycelium intertwines - contrary to what you see in the picture, and form clamp connections between the filiments or hyphae, this is mushroom sex.
Back to the method of determining contamination.
most mycelium of fungus are off white, grey, or brown but only slightly so. With time you will be able to spot contamination simply by the way the hyphae grow, crookedly, in a non-uniform manner. Cubensis will grow fluffy, that is until it becomes dicharyotic and then it may become ropey, in fact the "ropeyness" is a good indicator of it's ability to fruit, this is called rhyzomorphic.
But the real clue will come the instant your contamination gets ready to sporeulate. Spores contain the majority of color in mold. Most molds will create spores in an orderly fashion, in a circle as that particular portion of mycelium becomes mature. What you will see is a small circle of white with a pinpoint of green, in a few hours that pinpoint of green will grow larger while the white surrounding it grows even larger, whereupon THAT white turns green and the circle of white grows again.
the sooner you identify that color, no matter what color that is, the sooner you know for certain that what you have in the jar is not what you want. Throw it out, don't open it, don't shake it, the jar cost you a buck, the grain 20 cents, your opening it even for the tiniest of moments could well cost you your grow.
So, in short, any color - red, green, blue, black, rust, etc is never ever what you want. If you think that the blue you see is just bruising, simply wait 24 hours, if it has not grown, you are fine.
Study some of what you know is good mycelium for a bit, really look at it, perhaps with a lense. You are far better served by knowing exactly what your desired mycelium looks like than knowing all of the others.
But here is a short list of the bad ones:
Bacillus: This is bacteria, called "wet spot" it is very common, you will see a certain slimy, slightly yellowish spot on your grain. Where the grain touches the jar it will look wet. You may also see milky gray ridges growing around the larger colonies. Cubensis mycelium will not grow on top of this stuff but may well coexist with it. So you will see spots where the mycelium will surround this stuff and seem fully healthy. It is possible to bring substrates with isolated colonies of bacillus to fruition but it is a bad idea, as the endospores from Bacillus are pervasive and will tend to infect further attempts at growing spawn. This stuff grows mostly on agar and on grains. Oh, and if you are ever unsure, take your jar outside and crack the lid just a bit, if yuou smell rotten apples, or some say burnt bacon, then you have a case of bacullus, throw the jar away.
Alternaria:
This is a mold, it is very common and tends to grow on rye grain in the fields. It will also grow on leaves, rotting fruit, and straw. If you look at a bail of straw that has been left out in the rain, that brown/grey color on the bail is likely alternaria. the spores are black and it won't take but a second or two to determine if your grain in the jar is contaminated with this mold.
Aspergillus:
Aspergillus is everywhere. It will grow on any substrate from casing to grain to straw but it prefers neutral to slightly basic PH, which makes it just a bit easier to contend with. Asperrgillis can be seen as having tiny fruiting heads even with the naked eye, there are a large variety of aspergillus, some are quite dangerous, the colors of the spores range from green to black (niger) to yellow (flavus) to clavatus (blue-green) to fumigatus (grayish green) to "versicolor (green, pink or yellow).
The yellow one, Aspergfillus flavus produces a deadly toxin. Aflatoxin from this mold is the most potent hepatacarcinogen in the world. Flavus grows on almost all grains. The toxin however is not taken up by the fruit of the mushroom - still, you should have long before thrown out anything that has a slightly bushy appearance and is yellow.
Botrytis:
You will find this very grey fungus growing on overly wet casing where it grows very rapidly and will eat your fruit before you ever get a chance. Curiously Botrytis is highly prized when it infects grapes as the wine produced from such infected grapes is sweet and full of intense fruity flavors.
Cladosporum:
A dark green to black fungus that grows predominantly on spawn preparations - especially popcorn. The mycelium is highly branched early on and this is often visible to the eye.
Dactylium:
this is commonly called cobweb mold or soft mildew. It will grow on your casing. I is very very fast growing and even a tiny bit of the hyphae will start a new colony. Typicaly it starts on underpasteurized casing or areas that have little or no air circulation. the mycelium is greyish and sparse, billowy, delicate. It can be controled by aplications of salt or baking soda, you will not be able to stop it but you can control it long enough to get a flush in.
Fusarium:
It will be a bright yellow and will grow in your grain. IOn many cases this one is tough to identify in your spawn (grain) because it might not change color, otherwise it coud turn pink, or purple as well as yellow. Careful, this one can be highly toxic. It causes what is known as "Staggering Sickness" lending tot it's victims vertigo, bleeding, headaches, chills and nausea. In Russia during WWII a single outbreak eminating from stored grain it killed ocver 30,000 people. It grows mostly on casing.
Lateritium - pink
Avenaceumn - red
culmorum - yellow
poae - violet
oxysporum - red violet
If you see anything like this, don't mess with it , Throw the jar out, if you can, sterilize the jar intact before - you throw it out.
Geothrichum:
Lipstick mold, mostly growing on compost or casing
Monilla:
it is either a fine, powdery whitish mold - possibly looking like flakes of off white paint. Some say it looks like finely ground pearlite - one reason I never ever use pearlite in my casing.
Grows on your grain mostly but can start up on the sides of your cased trays.
Mucor:
this is the one I commonly mistake for bacillus - because the results of bacillus look mucorish, if that makes any sense. this is called black pin mold and you will see tiny black pinheds standing in the center of a contamination of mucor. This grows predominantly in grain or spent compost. you may see it after 3 or more flushes from grain starting in areas where there is little air circulation.
Penicillium:
Come on, you all know what this one looks like. The problem is that it is everywhere people who eat fruits and veggies are, it may well start on your mushroom debris so get rid of your bits and pieces.
Rhizopus:
Another pin mold, this one grey, will grow on your grain and on the margins of old grows.
And finally
TRICHODERMA:
Forest green mold. this is the one most likely to get you when you have done everything right. Colonies of this can crop up on your casing - keep your grow long enough and it WILL crop up, it does not grow that fast and you can control it with salt or baking soda but that is usually only a temporary fix. If you grow mushrooms for any length of time this one will infest your house. The spores are sticky and will cling to mites, some mites are drawn to this stuff so even your filtrations systems may not stave it off if you have mites. Af first the mycelium will be very difficult to tell from the one you are nurturing but it won't take but a day or two before it turns emerald and then forest green. An outbreak of this will usually signal the end of your grow. It's time to clean everything and start again. It prefers a ph between 4-4.5 and maybe a little higher so this is how you manage to keep it from growing. Your mushroom will continue to exude chemicals that will acidify it's surroundings, eventually it will bring the ph of whatever it is growing on into this range... So, the more basic you start your casing out as, the longer you get before trich arrives - just so long as you don't go too basic such that the mushroom itself won't grow.
Anyway, those are the most common.
