Accent color of Wat Phalat, on the Pilgrim's Trail to Doi Suthep

Maejo University -- Mushroom Cultivation Training + Sustainability Program

Maejo University is an agricultural university on the outskirts of Chiang Mai. The campus is large and contains many rather scenic agricultural installations but few people. 

We walk through one large building that seems completely empty except for cases of enormous insects mounted with pins. After hearing voices down a hallway, we knock on an office door and discover we are in the wrong building.

A man in the office redirects us to another nearby large white building, where a similar process repeats. I lose the specifics here, as all conversations have been in Thai.

Eventually we find a young man who is knowledgeable about the mushroom cultivation/education program, though I didn’t catch his actual position. At this point, all program specifics and questions are being translated and this kind of mediated conversation invites imprecise language and some inaccuracy, so some details may reflect that.

The mushroom cultivation area consists of a large covered platform with a pile of substrate, wood or coal-fired steam sterilization stations, and a series of concrete huts. The substrate in this case is rubber tree sawdust, lime to lower the pH, and likely some other nitrogen source. The University experimented with a few different types of substrate ranging from other types of sawdust, rice hulls, sugar cane bagasse, and straw, but settled on rubber tree sawdust because the mushrooms seemed to grow the best on it. All substrates are sourced from local agricultural waste— when a professor at Maejo later describes the program, he emphasizes the focus on sustainability and rural poverty reduction.

The program is rather clever, with a three-fold impact.  The first impact is the reuse of agricultural waste products, the second is the production of a nutritious and popular food resource, and the third is the creation of an accessible education resource so farmers can fully apply mushroom cultivation practices on their own. The University produces mushrooms and refines the process based on available materials, holds workshops that allow local rural farmers to grow their own mushrooms and purchase pure cultures from the University lab, and sells pre-made inoculated bags to local villagers who don't have the resources to have a full growing operation. These bags sell for 7 baht each, and can produce (in best conditions) 5 flushes of mushrooms, each worth 12 baht, giving the producer ~50 baht of profit ($1.60) per bag.

The young man leads us through their cultivation system, naturally starting with substrate and ending with growing sheds. Notably, this operation is geared towards primary decomposers and doesn't require the substrate composting like farms growing Agaricus species. This makes for a simpler process. 

Substrate and steam pasteurizing equipment. Substrate was mainly rubber tree sawdust.

Ash chute in the sterilizer -- a wood/coal fire heats water into steam which is funneled into industrial drums containing bags of substrate

Bags of sterilized substrate, ready to be inoculated

Pure culture of various strains. Pieces of the "parent" bottle are used to inoculate other bottles (containing agar or potato dextrose substrate) to maintain the same genetic strain. Pieces of the "parent" bottles are also used to inoculate bottles of millet seed which is then used to inoculate larger bags of growing substrate.

This strain exudes a dark liquid. Each strain/species' colony looks a bit different. I'm not sure which species this is, as bottles were grouped and labelled in Thai.

Millet seeds are inoculated by pure culture. The fully colonized seeds are then used to inoculate the bags of substrate. Colonized millet is also sold to farmers who make their own substrate bags. The quality and purity of a strain is a critical part of mushroom farming.

Closeup of myceliated millet.

Inoculated millet seeds visible at the top of a recently sterilized bag of substrate.

"Front" of mycelium as it grows throughout the substrate, top to bottom. It may take a week or more to get to this point. Probably a Pleurotus species.

A particularly beautiful growth pattern. Species uncertain.

Fully colonized bags, ready to be placed in a temp/humidity (semi)controlled room for fruiting.

A stack of bags in the fruiting room.

Fruiting. Because of inconsistencies between common names, scientific names, labeling, and translation, I'm refraining from naming most of the specimens pictured in this post. For example, these were labelled as "Grey oyster mushrooms, Pleurotus sajor-caju (Fr.)Singers", but according to the Wikipedia article referencing a Stamets book, cultivators commonly call warm-weather varieties of Pleurotus pulmonarius this name even though this species doesn't realllly exist as a separate entity and the actual P. sajor-caju was moved to the Lentinus genus... but there was also a Lentinus species in the same room though I don't think it was L. sajor-caju. Again, I'm going to refrain from labeling so I don't perpetuate any incorrect information.

Underside detail

The product.

Consequences of some form of bacterial contamination.

Another product.

Product in situ.

Ganoderma spp. (lingzhi) growing in a dark shed. The spores are used in cosmetics and the fruiting body is made into a tea popular in Asian traditional medicine. 

They take a long time to grow, but produce an abundance of spores. Spores and fruiting body command a relatively high price.

 While this operation seems successful in terms of producing mushrooms and providing accessible education and resources, there are some hurdles to the implementation of low-tech agricultural waste to mushroom programs. First, the strains themselves have to be sourced and maintained. In large-scale production operations like Phillips in PA (see earlier post), the pure culture strain is carefully selected for efficiency and quality, and the initial plates of culture are frozen in liquid nitrogen to maintain the earliest culture and avoid strain degradation. While a huge amount of mushroom culture can be made from a tiny amount of mycelium, this mycelium is not immortal, and if you culture the culture of a culture (etc.) the strain can start to deteriorate over time. Liquid nitrogen storage is simply not available in low-tech or small scale operations. While at this scale strain degradation can be less of a problem simply because less mycelium is produced, "parent" cultures are maintained and bags are inoculated vertically from the "parent" cultures rather than horizontally. This reduces the opportunity for contamination as well.

Another major concern with the reuse of agricultural wastes is substrate contamination. While fungi can often break down carbon-based contaminants, they are also capable of accumulating metals. If a metal-containing pesticide is applied to a crop, and the crop is then used for mushroom production, it is possible that the mushroom will be contaminated as well. It is notable that rubber trees are sometimes treated with arsenic trioxide (pesticide).



Thank you achaan Morakot for your kindness and generosity during my time in Chiang Mai.

Mushrooms in my second day of Thai food

I'm not in the habit of taking pictures of meals and it's not something I'm skilled at, but it seemed appropriate given the circumstances.

Straw mushrooms (Volvariella volvacea) in a soup that cleared my sinuses and led to the bottom of my 2nd (of 5) liter of water

Enokitake (Flammulina velutipes) wrapped in bacon, and grilled king oyster (Pleurotus eryngii). This stall at an open-air market also had steamed oyster mushrooms (Pleurotus spp.-- these oysters had morphological differences including a narrower base compared to the ones I'm most familiar with, which may be a result from different growing conditions, or they may be a different species than P. ostreatus, hence the "spp."). I was considering trying to ask them where they buy them, but they were doing pretty swift business. Maybe next time.  All varieties they were selling are commonly commercially cultivated anyway, so there probably wasn't much info to glean.

Interesting note about enokitake: they are grown in particular controlled conditions (likely no light, maybe controlled CO2) that make their appearance vastly different from wild individuals of the same species. If you google the species name, you'll find very little resemblance between cultivated and wild specimens.

Hed paw - a source of admiration, pollution, and naming confusion

On the plane from Bangkok to Chiang Mai yesterday, I sat next to a friendly American expat, Craig, who mentioned that the hill tribe people do semi-controlled burns that have something to do with mushroom collecting. He googled it on his phone before takeoff, and confirmed that the burns are set to facilitate the collection of "hed paw/hed tawp," some sort of semi-buried mushroom that isn't cultivated and can be sold for high prices (source). While these mushrooms are highly sought after, the unpopular burns conducted to find them are blamed for some of the air pollution in the area.

Mature Astraeus sp.

Based on this initial description, I expect these fungi are mycorrhizal (hence practically impossible or economically unfeasible to cultivate). The brief and vague description reminded me of morels, which are mycorrhizal, not commercially cultivated, expensive, and are found in great numbers after fires. I asked Keith, the friendly British expat guesthouse proprietor, if he was familiar with any of the mushrooms sold locally, and he spoke highly of some sort of brown, round, lumpy mushroom, sometimes called the Chiang Mai truffle. He said they are very seasonal (suggesting that they aren't cultivated), and I expect that these brown lumps are the "hed paw" mushroom.

Immature Astraeus sp. - when they are eaten

After a bit more googling, it looks like the mushroom is a "false earthstar" (Astraeus spp.), a widely found genus of mycorrhizal fungi. One source that discussed the mushroom in the context of the slash-and-burn approach of the hill tribes called it Astraeus hygrometricus, though this name was given to most similar Astraeus species globally and represented a species complex until the early 2000s. According to Wikipedia, molecular and morphological evidence indicates that Thai Astraeus species previous lumped under the name A. hygrometricus include Astraeus asiaticus Phosri, M.P.Martín & Watling (2007) and Astraeus odoratus Phosri, Watling, M.P.Martín & Whalley (2004) syn. thailandicus Petcharat (2003). There is some uncertainty about whether the burns are set to clear the underbrush and make the mushrooms easily visible or if the fire itself triggers a flush of fruiting, as with morel species. For more info, one of the Wiki sources (a 2004 Mycotaxon pub, "The genus Astraeus in Thailand") is free access. The excellent Cornell mycology  blog also did a post about Astraeus species in North America v. ones in Thailand very recently that does a better job of describing the problem with naming within the Astraeus genus.

Interior endoperidium brown with spores forming; exoperidium splits into a star shape when mature, and lifts endoperidium above leaf litter to eject spores.

I trotted downstairs and asked Keith if the image on the Cornell blog matched the mushroom he was fond of, and he confirmed that it did. Raitree, a Thai woman and the other proprietor of the guesthouse, quickly named it in Thai -- "hed paw" indeed. She then called one of her friends who said the season ended two months ago in May, but I'm still going to keep my eyes peeled for brown lumps (and other mushrooms) at the Sunday market.

UPDATE- 9/8, found some Astraeus sp. (tentatively ID-ed, pictured above) in Ban Tak. A local called it "het thawp," suggesting it is the species that they consume when immature.