mycorrhizae And antifungals

Drjd

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I wanted to post this question because I have yet to read much that addresses this topic. Mycorrhizae are important for many tree species and particularly pines. In order to keep prevent and/or treat fungal infections I have read to use certain a antifungals, but my concern is killing the mycorrhizae. I am aware that certain antifungals act on different fungi, and that is likely why it can be safe to use antifungals, but are there any antifungals I need to strictly avoid? Has anyone ever had any issues with this?
 

Shibui

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IMHO the importance of mycorrhiza has been blown out of proportion. Mycorrhiza does assist many species to obtain nutrients, especially in harsh and poor soils but trees can grow without them. Where nutrients are readily available the importance of fungi diminishes as available nutrients are taken up by normal roots.
In my experience mycorrhiza readily colonizes from one pot to another without any help. All my pines, including seedling trays, end up with thriving fungi in a matter of months so killing some with fungicide does not worry me at all. Even if I do kill some it will be back soon.
I would expect the fungicides that treat leaf infections would probably not be too detrimental to soil growing fungi. That would include copper and lime sulphur based sprays.
The ones aimed at root fungi like phytopthera and any that are systemic are more likely to affect mycorrhiza.
 

Harunobu

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I think most people just like to use a fungicide so they feel they did something good for their bonsai. You can always check the active ingredient of the fungicide. There are broad spectrum fungicides. Yes, they should also be killing mycorrhizae. But then there is a debate about what happens when you apply a fungicide on the leaves. And if that affects the mycorrhizae that grows partially inside the roots of the bonsai.

An analogy with our own human gut flora/intestinal microbiome is an analogy, but not a very far fetched one. If you take a broad spectrum antibiotic, you are likely to suffer from antibiotic-associated diarrhea caused by C. difficile. Is it safe to kill a lot of your cut flora? Is it safe to kill mycorrhizae? Does preventative fungicide on bonsai make sense? The soil microbiome is different, but analogous. What exactly that means, I don't know.
 

Mike Corazzi

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Well, it was certainly impressive even if unexplained.
 

Wires_Guy_wires

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Myc can certainly die from antifungals, and some might never come back due to remaining traces and the fact that other organisms have colonized the substrate and produce their own antibiotics to keep competition at bay. Copper can have long lasting effects and inhibits all fungal growth to a certain extent.

Antifungals come in two forms: precise action meant for specific fungi - which are "broad spectrum" in the sense that they do a lot of collateral damage to fungi we haven't studied (either because they're hard to study, or because they're unknown, or because they're beneficial and don't require studying because they pose no economic risk).
The other form is broad spectrum - meant/designed to kill all fungi, no matter their shape or form by attacking mechanisms that are common in all fungi. Naturally with a bunch of collateral damage.

Some, if not all, antifungals affect bacteria, yeasts and archea too. Those are also important parts of the plants microbiome.

Plants can live in a perfect sterile environment if the right nutrients are provided, they don't always need myc. And over time, when antifungals break down the pots will recolonize fairly quickly, the composition and species variety will never be the same as in untreated soils though.

The key issue is that antifungal resistance can be passed on between different fungi. This is a process called horizontal gene transfer: instead of evolving in a tree-like pattern by making offspring, resistance genes can be transferred horizontally from branch to branch (on the evolutionary tree) in some cases. Instead of evolving in the traditional sense (generation passes on to the next), they just take genes from resistant organisms and incorporate those genes into their own DNA. This process is poorly understood in fungi, because they're a pretty unique type of organism by themselves. Prolonged exposure to antifungals can cause this to happen, sometimes with serious outcomes for us humans (resistant Candida outbreaks for instance). The process is reversible too; if genes aren't used enough, they can be shedded in a few generations because they become "dead weight".
Treating your plants for longer periods increases the chance of resistance to occur.

In pines and other conifers, we're dealing with long living myc. Fungi that can live for decades, if not longer. These don't shed genes easily and they don't evolve fast (although they can take up new spores and can form some kind of super organism with multiple nuclei from multiple parents). The plus side is that if they become resistant, the resistance will last for a long time. The downside is that this resistance can spread, and that it might take a very long time for resistance to occur in the first place. The competition is still the competition after millions of years, because they evolve as fast or faster than the good guys. It's an arms race with no end.

Personally, I try to stay away from antibiotics with the exception of lime sulphur for wood and copper sulphate for foliage applications. There are a multitude of first line options - peroxide, beneficial micro organisms, protective fungi, adaptations to the soil, or just removal of infected parts - and antibiotics are my final line of defense if all else fails. I have used them once in the past fifteen years of gardening.
Thus far, preventative measures have been enough. I have roughly 140 pines and I find +/- 40 needles with needle cast every season, I just pluck those needles off. Soil borne fungal issues are rare in my back yard and if they happen it's most likely because I created the conditions for them to happen.
I try to keep diversity high; every micro-organism produces its own antibiotics to fend off competitors, and this can help prevent much of our problems with no human interference.

I'm trying to "graft" myc too; use a wooden peg or a piece of cardboard, let it be colonized, transfer to the next pot. I also catch some runoff water from healthy trees and distribute it across the rest, since bacteria are more water bound. This however can bite me in the ass at a certain point; I could also be spreading disease. But that's a risk I'm willing to take.

I'm not against antibiotics, but I've seen in the lab what happens when resistance occurs. So I use them with caution, and when I do use them I make sure they leave no witnesses.
 

Clicio

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If I have to apply fungicides to conifers I do cover the soil during spraying and let it be covered till next watering.
Then I take the plastic protection off the soil and water just the substrate, not the needles.
 

sorce

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think most people just like to use a fungicide so they feel they did something good for their bonsai

I feel they want grandkids with 4 testicles 6 ovaries and a dinosaur toenail.

Sorce
 

LanceMac10

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I wanted to post this question because I have yet to read much that addresses this topic. Mycorrhizae are important for many tree species and particularly pines. In order to keep prevent and/or treat fungal infections I have read to use certain a antifungals, but my concern is killing the mycorrhizae. I am aware that certain antifungals act on different fungi, and that is likely why it can be safe to use antifungals, but are there any antifungals I need to strictly avoid? Has anyone ever had any issues with this?



@markyscott put together this fine resource...last installment in a three part series. https://www.bonsainut.com/resources/dormant-season-spraying-part-3-pine-trees.38/

As his climate could be considered similar to yours, maybe you could peruse the articles. That could be a fine start, as he has a lot of experience to offer.

Most treat-able fungal are likely leaf based and can be controlled with a copper based solution. I do cover the soil surface for piece of mind but I'm not sure it would make a difference.
Anything worse than something like needle-cast and I would just dispose of the material wholesale....
 

cmeg1

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IMHO the importance of mycorrhiza has been blown out of proportion. Mycorrhiza does assist many species to obtain nutrients, especially in harsh and poor soils but trees can grow without them. Where nutrients are readily available the importance of fungi diminishes as available nutrients are taken up by normal roots.
In my experience mycorrhiza readily colonizes from one pot to another without any help. All my pines, including seedling trays, end up with thriving fungi in a matter of months so killing some with fungicide does not worry me at all. Even if I do kill some it will be back soon.
I would expect the fungicides that treat leaf infections would probably not be too detrimental to soil growing fungi. That would include copper and lime sulphur based sprays.
The ones aimed at root fungi like phytopthera and any that are systemic are more likely to affect mycorrhiza.
Yup!
Seems it is only needed when no available phopherous( or rock phosphate or something that is organic source) If the ion is available from say soluable source like mono ammonium phosphate ...the roots will actually expell the myco for a pathogen..............now let us not forget that microbes are a whole different thing in that even in soluble fertilizers or(chemy) if added regularly they will be totally viable as long as humates or molasses are added to to feed them....they will eat root exudates and make npk in amino acid form???
At any rate they lessen the load of energy producing that the leaves have to do photosynthetically........and actuall enable the leaves to have a reserve and attain higher brix(suger) for vitality and essetial processes.
Microbe produced npk is excellent!!!!

Myco is needed to break down phospherous in organic sourced phospherous.
Because my hydro teacher told me so
 

Paradox

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There are more than a few of us that need to apply fungicides to pines throughout the spring and summer to prevent fungal infections on our trees.
Unfortunately in some places, its unavoidable.
I cover the soil of my trees with some old towels I keep for that purpose and remove them once the treatment has dried on the tree.
 

Jzack605

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I only looked at the highlights. But it seems systemics will have an effect while contact applications will have minimal effect on mycorrhiza.
 

Drjd

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@markyscott put together this fine resource...last installment in a three part series. https://www.bonsainut.com/resources/dormant-season-spraying-part-3-pine-trees.38/

As his climate could be considered similar to yours, maybe you could peruse the articles. That could be a fine start, as he has a lot of experience to offer.

Most treat-able fungal are likely leaf based and can be controlled with a copper based solution. I do cover the soil surface for piece of mind but I'm not sure it would make a difference.
Anything worse than something like needle-cast and I would just dispose of the material wholesale....
Thank you this is great!
 

hemmy

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Bnana

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It is important to distinguish between the different groups of mycorrhizae, Ecto- AMF and Ericoïd. They are very different from each other.
In bonsai the role of mycorrhizae is often exaggerated. Under natural conditions trees compete for nutrients with each other, they do not do this in our pots.
They will be there and will do some things but are much less relevant than in natural, nutrient poor, forests.
On the other hand a lot of fungicides are used when not necessary.
 

hemmy

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