Shiitake Mushrooms Infected by Mould
Answered by: Bill Chalmers
Question from: Trudy Van Grootel
Posted on: May 27, 2007

I purchased a kit from you. The one on a saw dust substrate (not the cells) I soaked it, tented it and poked holes for aeration as per instructions. We have a cold room with a window and I ran a fan. Mushroom buds appeared in days. I had a beautiful harvest and more buds were appearing. The block was still moist -- BUT THEN ... mold appeared! I added no more water then the original soaking instructions. I let it dry out a bit and washed the mold off. (My cold room is clean and has no musty smell). I checked it and it was very light and dry and all productivity stopped, so I resoaked it re tented it in a clean bag and poked sticks in the block to keep plastic further away from block.

It’s difficult to come up with a pat answer for this, so I am just jotting down a few thoughts as I read and re-read your note.

Where they are, and local conditions like temperature and humidity, the amount of dust in the air, etc. may be factors affecting how things go, and of course they change with the seasons. Shiitake needs at least part of the day around 15C for "pins" (mushroom initials) to form. There was likely no need for a fan for a single block in a large room and a fan might promote too fast drying as well as stir dust and spores up. Letting the block dry out a little under cool (10-20C) conditions should not injure it, nor should rinsing the spores off. Poking sticks in the block could carry the surface mold into the interior of the block but that would likely only cause problems over a longer term. You mention soaking the block but make no mention of whether the block actually absorbed any water. Often the rind which develops on the surface of the block acts as a barrier to water. When the block is soaked (must be COLD water) it may need to be forced under the water with weight and may need to be soaked up to 6 or 8 hours (the water MUST be cold) or soaking for shorter periods repeated over several days. It’s not appropriate to remove the rind, although if all else fails a few shallow slits might be made in the block. The point of soaking is to raise the water content of the block, so there should be an obvious increase in weight.

[Follow up from Trudy Van Grootel:]
Thank you for your reply..It helps me understand this better. I cut off the 1/3 top portion of the block (as it was soaked ... black and rotting) and so far ALL mold is removed. I need to promote pinning and I think I will have a salvagable block.

[Further thoughts from Bill Chalmers:]
A week later I have a few more thoughts on this. I wonder if she may not be keeping the blocks moist enough after soaking them. More attention is necessary for this than was the case for first flushes and it will be more critical now with the warmer drier weather. After soaking do not let the substrate surface dry out until there are well developed pins evident. Also do not try to rush the packs between flushes. They need a minimum 2 weeks resting but not more than 4 weeks. This is temperature dependent. The longer time at cooler temps (15C) and the shorter time at warmer temps (25C).

[Bill Chalmers is a mushroom expert grower who kindly agreed to answer this question on behalf of Richters. --Ed.]

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