Using fungi to detoxify persistent herbicides inside greenhouse?

I would really like to grow mushrooms (King Stratophoria?sp.) on my hugel beds and flat growing areas(straw mulch) along with my garden crops. The problem is the only straw I have access to doesn't have a weed in it.... leads me to believe there are plenty of persistent herbicides present. Would those mushrooms be Ok to eat or should they just be composted? I've been using my greenhouse (poly hoop) to house my chickens all winter with a deep mulch of the same straw. I was hoping to use this for mulch this season as well. I'm just a little concerned about the pesticide residue. Maybe it should all be composted for a year then be useable, just seems like a waste of fine chicken crap! The reason I'm asking here is that I know Zach is a greenhouse enthusiast, and I believe Sepp would appreciate the stacking of functions, but if it belongs someplace else feel free to move her on out.

Dave Redvalley wrote: Would those mushrooms be Ok to eat or should they just be composted? I'm just a little concerned about the pesticide residue.

Let me clear up a little confusion about how herbicides and pesticides move through the food chain. It is true that animals and plants can ingest these compounds and whatever eats them has ingested them as well. This is not the case with fungi. Fungi have no stomachs. When fungi find something they want to eat, they secrete digestive enzymes which break the food molecules into smaller pieces, then they ingest it. The only way they are going to pick up herbicides or pesticides is if they have broken down the molecules first into something they can use. But then these molecule remnants no longer have their pesticide or herbicide properties.

The only way that mushrooms are going to pick up "residues" is by inadvertently growing around them. For example, after a heavy rain, mushrooms can grow to large size overnight, and in the process grow around little bits of grass, leaf litter, small sticks, etc. If the residue is in these pieces of debris, then it is in the mushroom. But if you clean your mushrooms well before you cook them, you are going to remove all that debris.

This is a really great question, and one that I don't know the full answer to. I take the approach of avoiding persistent herbicides at all costs, as I don't have a good strategy for dealing with them. I have been told by University students studying "Sustainable Foods and Bio-energy Systems" (they learn a ton about chemical agriculture but nothing as far as sustainable techniques) that the half-life of the herbicides and pesticides on the market today is mandated to be pretty short. They were under the impression that after a year, the majority of the chemical is no longer active. If it were me I would have some samples tested before consuming anything. If this is too expensive then observe if the wild animals consume them or not, they have much more acute senses than we do.

John, thank you for the wonderful explanation. I understand that fungi are very different from animals in that they digest compounds before accumulating them. If they are only ingesting compounds that they can use how is it that heavy metals, hydrocarbons, and radiation are accumulated in the fruiting bodies? Perhaps they are trying to purify their environment by removing these toxins? Why wouldn't there be the same risk for accumulation of herbicides and pesticides?

Dave, if I were in your shoes I would remove the contaminated straw and continue to work with the material as a remediation project outside the greenhouse.

Some really good research has been done into oyster mushrooms cleaning up oil spills. Just as has been mentioned previously these extracellular enzymes can break down complex long chain hydrocarbons, literally cleaving the bond between carbon and hydrogen atoms creating carbohydrates in the process to be used as food. Though the mycelium does take on color of oil initially, it and the rest of the growing medium is rendered non-toxic after 12 weeks give or take depending on concentration. Mushrooms also accumulate heavy metals so that's something to take into consideration. Stropharia rugosoannulata aka king stropharia or garden giant has quite an appetite for bacteria and has been used to capture and filter runoff water from animal pasture. So I'm not sure what mushroom would be best at breaking down pesticide/herbicide but as many of these are created using petrolium distillates I would personally go with oysters.

Much of my knowledge base on mycoremediation comes from Paul Stamets, a true mycological pioneer, very worth while to check out his talks/vids for anyone who feels the earth as many here do.

Zach Weiss wrote:
John, thank you for the wonderful explanation. I understand that fungi are very different from animals in that they digest compounds before accumulating them. If they are only ingesting compounds that they can use how is it that heavy metals, hydrocarbons, and radiation are accumulated in the fruiting bodies? Perhaps they are trying to purify their environment by removing these toxins? Why wouldn't there be the same risk for accumulation of herbicides and pesticides?

Heavy metals and radiation are much different chemically from hydrocarbons and other organic molecules. Metals and radioactive elements are atoms, and all the digestive enzymes that fungi throw at them cannot change their atomic identity. Hydrocarbons are a subset of organic molecules, and these are all broken down by fungal enzymes and detoxified in the process. Herbicides and pesticides are highly modified organic molecules, and they are easy pickings for the digestive enzymes of fungi.

Now there is a grey area, that where a metal atom is chelated in a cluster of organic molecules -- think hemoglobin as an example. When fungi are digesting the hemoglobin in a drop of blood spilled on the ground, they end up absorbing the iron along with the other organic fragments. This goes a long way to explaining heavy metal and radioisotope uptake by fungi.

This is a great question.

I have avoided commercially grown hay and straw for this very reason. The one time that I did purchase some straw it was a disaster. Nothing grew in that spot for almost a year.

Is there a way to 'detoxify' commercially grown hay or straw?

Jeanine Gurley wrote:
Is there a way to 'detoxify' commercially grown hay or straw?

You could use straw mushrooms. I know you have a greater selection of Asian markets up in Columbia than we do in Augusta, maybe they have some fresh straw mushrooms that you can use as inoculate (canned won't work, because canning sterilizes the mushroom spores).

A second possibility would be to use regular grocery store mushrooms, which are known to mycologists as Agaricus Bisporus. It's more of a field mushroom, and the more manure in the field, the more likely you are to find them.

Whichever mushroom you decide to use, the method is the same: blend the mushrooms up with some water, mix it in with your pile of hay or straw, and then keep it well watered. After 3 or 4 months, your pile should be significantly detoxified.

Great information here guys, thanks for the feedback. It seems like the fungi will probably break down the herbicide residues, but I should set the straw aside for a season after I inoculate it to be on the safe side. Does this sound right?

Mushrooms aside I like the idea of chickens in the greenhouse over winter. Did they give much warmth to what ever you grew over the winter?

Dave Redvalley wrote:Great information here guys, thanks for the feedback. It seems like the fungi will probably break down the herbicide residues, but I should set the straw aside for a season after I inoculate it to be on the safe side. Does this sound right?

In your climate, fungal activity stops for the winter, so yes, you might want to wait until next season to use it. But if you got a good start on the inoculation in the spring, you could use it to mulch in the fall.

Brandon
I didn't try to grow anything in there this winter (first winter). I did notice that once the deep litter started to compost with all of that chicken poo the lowest temp I saw was 14F with the outside of -14F. The biggest benefit I've noticed is reduced feed for the chickens. They get yo roam around a and scratch an hop around a lot more than of they were couped up or trying to do all of that in a couple feet of snow and ice.

I bet and all that liter and shit where you need it. I am by no means an expert but in my pest mangiment class we learned that there are few real persistant pesticides left on the market. There are those that break down slower than other but compared to pestisides (herbisides) of old they don't last near as long. I wish that they weren't so readily used though you have to worrie about most free or cheap mulch because of it.