Per Lisa‘s request – here is a quick description of mushroom farm trip in October.
There are several indoor mushroom farms in the US. We got to visit a farm outside of Watsonville – Monterey area 1.5 hours south of the SF Bay area. The class was able to visit because John knows one of the research scientists, Steve, who works for Monterey Mushroom farms. We had to wear hair nets for health code reasons, although ignore the fact that the mushrooms grow in a pile of compost (which IS heated to a suitable temperature to kill most of the nasties).
The compost piles are actually quite amazing as they have a delicate system of monitoring the temperature and moisture content of the piles. They are frequently turns to insure good air mixture and are watered with a collection of nitrogen rich liquids (can you imagine where that might come from… such lovely smells…)
Primarily the farms grow Agaricus bisporus (bi-sporus because it produce two spore chains instead of four like most Agaricus). Tom Volk of course has more to say about these mushrooms. They also grow Pleurotus ostreatus or oyster mushrooms.
The white and brown A.bisporus are the same species. It may only be a few genes having to do with lacasse The brown ones you see at the store are often called Crimini but they are the same species as the white button mushrooms that go on your pizza or in your mushroom soup. Portabello mushrooms are just Crimini which has been allowed to grow larger. They typically prune the mushrooms around one they will want to make a Portabello and allow it to grow longer. Mushrooms can be re-picked up to three times before the soil has to be thrown out. If the pickers are careful sometimes a bin can be up to five times, but each time there is a picking there can be problems with mites and infections so often by the 3rd time the size and health of the fruiting bodies are reduced.
Apparently one of the large growing rooms, which has a stack of 5 – 6 tall boxes, 6 of these stacks in a row, and ~50 rows (I think) can generate $100k a month in mushroom sales. I think it works so well because a) they have a lot of good workers who do the picking b) they understand the science of the compost so well, c) they are one of the largest west coast distributors so they have contracts with a lot of places.
Steve also showed us a new hybrid mushroom they had made via crossing a wild strain with the monoculture strain that is grown. They had to do a lot of crosses to breed in the particular traits they wanted from the wild strain. The actually don’t have a lot of genetic resources, but maybe genome projects will come for Agaricus…
One problem with the monoculture is they can get infected with mites that can attack the Agaricus and reduce the production. They use a variety of techniques including an oil that is typically used to combat nematodes. It smells like rotten garlic, but it works. The hybrids may also provide additional resistance naturally.
The evening finished with some freshly picked portabello mushrooms fried up in my omelet. Definitely a different flavor when they are fresh.