Avoiding Contamination

Advice is free and easy to give, yet many only look for help when things go wrong, rather than before starting a new venture. There’s no shame in admitting we were guilty of this when we first started out growing mushrooms. After all, we’d grown all sorts of vegetables in the garden before and so we decided growing mushrooms can’t be any harder than that. Optimism is a great thing but, sometimes, listening and reading can be even better!

We can’t agree among ourselves when we first tried growing mushrooms at home but we do know that very shortly afterwards we quickly discovered not only how enjoyable mushroom cultivation is, but also how frustrating it can be! We’re not bald just yet but considering how much hair got pulled out, that’s actually quite remarkable! It’s no exaggeration to say that several of our first attempts at mushroom cultivation actually developed into green mould farms and, unless you’re willing to listen to a little advice before you get started, you could easily replicate our mistakes.

The most important advice we can offer new growers is to be aware of the risk of contamination damaging or totally destrying your grows. Learning how to identify contamination is very helpful as it can help you identify where problems occurred and reduce the risk of it happening again. It’s not the only advice you need, but contamination is the one thing that you simply cannot ignore. Crossed fingers just won’t do it.

The photo on the left shows what a green mould farm in a grow bag looks like. Better known as trichoderma, this is one of the things you don’t want to see when trying to grow mushrooms!

Advice on Contamination

How can contamination occur?

In most cases home growers will be using some form of sterile grain to get their mushroom growing started. This might be in grain bags, jars, grow bags or other containers. The grain will have been soaked in water, boiled and then sterilised in a steam autoclave or pressure cooker. If you think about it, while you might not choose to eat it, your sterilised grain is pretty much the same as cooked food. In the same way that if you leave cooked food laying around too long it will start to rot and attract mould, so too can sterilsed grain. Contamination can occur through obvious routes such as touching (your hands are nowhere near as clean as you’d like to think), mould and other spores floating in the air, flies and other crawlies, unclean surfaces, containers, water and so on. Even your breath.

What does it matter?

Mushrooms start their growth with the development of mycelium which, when all goes as planned, grows in and on your sterilised grain. However, when other spores or bacteria are present, it can easily be overcome by these contaminants. Most commonly you’ll see green or black mould starting to develop along with your white mycelium. These contaminants will quickly overcome the mycelium and colonise the whole container. If you’re not careful, spores from these contaminants will then escape and contaminate anything else they can reach – surfaces, clothes, hands and any other mushroom growths. Very soon, you’ll have your very own green mould farm.

Sterile Working Advice

Before you try growing mushrooms, our advice is to think carefully about how to give yourself a sterile working environment. You need an area where temperature can be kept stable, ideally where air is disturbed as little as possible and where you can keep surfaces hospital-clean. Your best friends will be a plentiful supply of 70% Isopropyl Alcohol, alcohol wipes, disposable nitrile gloves and face masks. These basic supplies will help you avoid the most common forms of contamination.

Surfaces: All surfaces where you plan to work with and grow mushrooms need to be cleaned with 70% alcohol (70% alcohol is better at killing contaminants than 90% alcohol). They need to be kept that way constantly and should be cleaned again every time to work in your mushroom work area.
Hands and gloves: You don’t want to be continually spraying your hands with alcohol (and it wouldn’t work as well as you’d imagine) so disposable gloves are essential. Wear them at all times when doing anything mushroom related, and keep them clean by spraying with 70% alcohol.
Face masks: It may seem like overkill but breathing on your work can help spread contamination, either by disturbing the air and blowing floating bacteria onto what you’re doing, or simply by the bacteria in your breath. A simple disposable face mask is a quick and easy way to reduce that risk.
Equipment: Any tools or containers you use should be sterilised too. In some cases this is actually hard to do as you won’t have a steriliser handy, but metal tools can be flame sterilised (a simple bunsen burner from amazon will do the job) and most other items can be cleaned with 70% alcohol.
During inoculation: When you inoculate your grain or grow bag with liquid culture to get the ball rolling, clean the injection port with 70% alcohol. Assuming the syringe and needle are sterile packed, they should be usable as-is. If the needle has been used before, it should be flame sterilised before using again.

Contamination Awareness

Mentioning contamination on our home page might not seem a bright thing to do but it’s essential that anyone considering mushroom cultivation is fully aware of the potential hazards and how to avoid them. It’s in your interests, in simple terms.

Like it or not, guarding against contamination needs to be at the forefront of every mushroom grower’s mind. Quite simply, the need to guard against contamination is part of the daily reality of mushroom cultivation. Myco Mojo growing materials such as grain and substrates are supplied to you sterile in heat sealed mushroom bags, but that sterility breaks down the moment you start to use them. As soon as products are opened, inoculated or otherwise used they need to be properly protected against the ingress of unwanted spores, bacteria and other contaminants either through touch, air ingress or through injection. We strongly urge all buyers to take all possible steps to reduce contamination risks prior to ordering products to avoid frustration.

More advice on mushroom growing can be found on growingmushrooms.co.uk in their ‘how to’ section.