What to do with a contaminated bag, block or tub

Extension sources don't give a home grower's script for a mouldy bag. They describe what commercial farms do. Those steps are a useful guide to the thinking, though not a recipe. Whether to keep a contaminated block growing isn't something the sources answer, and a grower's own kit instructions come first.

Dry bubble: hands off

Penn State's dry bubble control list says "Do not touch!"¹. The same guide separately lists vectors for dry bubble, including people with dirty hands and clothes, equipment and water¹. The source does not say how the two are connected.

Spot treatments on farms

For cobweb, Penn State lists covering infected mushrooms with a damp paper towel before applying salt, alcohol or gypsum paste¹. For dry bubble it says cover infected mushrooms with salt or spray alcohol¹. The warning is in the cobweb entry only. It reads: "Spot covering or removing infected mushroom may favor disease development."¹

These are commercial spot treatments for fruiting mushrooms on a farm. They aren't directions for a grow bag, and the source gives no instructions on whether any of this suits a home setting.

Spread by water and air

When a problem is already in the room, how you water matters. Penn State says that once bacterial blotch occurs, the bacteria are spread by splash during watering². For cobweb it says to turn off air handlers when watering an infected room¹.

On the blotch page, a chlorine dose is given for farm irrigation water. It controls blotch only if the mushrooms can be kept dry². A chemical dose like that belongs to commercial settings with their own safety rules, so it isn't repeated here.

What farms do about the room

A UK industry guide for Trichoderma aggressivum lists measures for farms. It gives no order. They come from two separate lists in the guide³.

• General list: where infection is detected, put specific precautions in place straight away and notify the rest of the production chain.
• General list: use end-of-process steam sterilisation, and test to make sure the infection is gone.
• Grower facilities list: restrict all but essential access to the farm.
• Grower facilities list: increase hygiene measures.

For dry bubble, Penn State also lists steaming early when infestations are heavy to reduce spore load on the farm¹.

Why the stakes are high

Green mould is one of the diseases Penn State's pest page calls prevalent among cultivated mushrooms, with significant yield losses possible in button, oyster and shiitake crops⁴. That's why the UK guide opens with strict procedures for all composters, haulage contractors and growers, at all times³.

What the sources leave out

They don't say how to throw out a contaminated block, whether a home composter is safe, or how to protect other grows nearby. Without a source, this site won't guess. For causes, see why contamination happens. For identification, see common contaminants.