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Microarthropod grazers?

Posted by Eliza Greenman 
Microarthropod grazers?
March 13, 2020 06:03PM
Hi Everyone!

This is coming out of left field, but I thought it could be an interesting adjunct to the discussion on Marssonina leaf blotch none the less.

I'm rennovating an orchard that is covered in an understory of autumn olive (Elaeagnus umbellata). I have had suspicions that the lack of diseases I've found in the trees might have something to do with the AO in the understory. After a few mornings of searching, there may be something to this and I wanted to share a documented connection with AO and Marssonina:


This article states that companion planting AO with Black Walnut controlled two fungal pathogens responsible for defoliation Mycosphaerella juglandis (septoria leaf spot)
and Gnomonia leptostyla (walnut anthracnose)). A little further digging and I found that the asexual state of Gnomonia leptostyla is Marssonina juglandis.

The control of these fungal diseases is due to microarthropod grazing, with numbers way higher in AO leaf litter than of just grass. When infected leaves fall on a bed of AO leaf litter, the tiny grazers control the diseases through consuming the perithecial bases of the leaf lesions and eating the ascomatal contents within, as well as consuming some portion of the dead tissue surrounding the lesion.

I know that Marssonina juglandis is NOT Marssonina caronaria, but I wanted to chime in with what looks to be a very interesting possible natural control. eye popping smiley


Edited 3 time(s). Last edit at 03/13/2020 09:06PM by Michael Phillips.
Re: Microarthropod grazers?
March 14, 2020 03:03AM
Decomposers on the orchard floor tied to specific plants provides a whole new perspective.

I recall research into fungal antagonists, Microsphaeropsis spp, that lessen ascopsore production from scab pseudothecia on apple leaves. This paper entitled Effect of Fall Application of Fungal Antagonists on Spring Ascospore Production of the Apple Scab Pathogen, Venturia inaequalis. details what's known in this regard. This is biology tied to apple leaves in natural settings. Still, I could see broadening that to microarthropods thriving on tree leaf cellulose and thus subsequent decomposition of disease organisms overwintering on mutual leaf litter.

But mostly I think the whole country is now going to be talking about how Eliza Greenman recommends planting Autumn Olive everywhere!

Lost Nation Orchard
Zone 4b in New Hampshire
Re: Microarthropod grazers?
March 14, 2020 02:17PM
I thought about this all day and talked with the only two friends I have who will listen and provide feedback to this sort of chatter. Here's a question and some further thoughts:

1.) What makes Autumn Olive leaf litter a hotspot for Collembola (springtails) and Acari (mites) to gather?

a.) My friend Nick suggested that he has seen Elaeagnus get mildews, and perhaps the early drop in infected leaves creates a primer for these fungivores that carries on into the winter. I haven't looked into the fruiting bodies of the mildews to see if any microarthropods dine on them. The question becomes: Is it fungal disease they are eating or is something being offered from the host plant (like hyphae)? Or is it both?

b.) From a book I have called "The Rhizosphere," it says: "Much is left unexplained about the distribution and movement of mites in soil, but they seem to be favored, along with Collembola, in the fermentation layer, that region between litter and humus."
I have found papers broadly suggesting that invasive leaf material decomposes much faster than native leaf material, and many of the invasives hold onto leaves much longer than the natives. I'm wondering if a bed of invasive leaf litter is then more welcoming to the microarthropods because it has a more active fermentation layer for a longer period of time?

With regards to everyone going out and mass planting AO in your orchard understory, the USDA did put out a publication in the early 2000s about it being the next cash crop! With pruning, you can harvest AO berries with an over the row blueberry harvester. Don't delay. Lycopene!
Re: Microarthropod grazers?
March 14, 2020 02:18PM
This hearkens back to what my PhD thesis would have been all about had I followed through. More importantly it speaks to importance and power of a biodiverse orchard ecosystem and especially the soil food web. The soil food web of course is not fungi and bacteria, but nematodes, protozoa, a whole slew of microarthropods, macroarthorpods, and higher order animals. They all depend on each other (in sometimes not so pretty ways) and in this case its the microarthropods that are taking care of the leaf litter (though I do have to wonder where Scott's worms fit in to all of this). I doubt the collembola have a specific preference for only one species of Marssonina (M. juglandis v M. caronaria) over the other, since they are also eating other parts of the plant and fungal body, it just doesn't seem evolutionarily appropriate to only feed on a single fungal species. As well, and this goes to a conversation I was having the other day, many species feed on mushrooms not just for sustenance but for health and immunity purposes (is there any difference). Paul Stamets has shown that bees feed on polypore mushrooms as a way to increase the overall health and immunity of the hive. And this makes total sense, as does the potential that the microarthropods and other members of the soil food also feed on fungi and bacteria not just for food but health and immune boosting properties. None of this should be a surprise to this group. What it does speak to is more micro-investigation of what's going on the soils profile. How biodiverse is your soil food web? How healthy is the supporting environment - pesticides, toxins, pollution, lack of oxygen, water quantity and quality? And then of course what are you doing to improve and support the soil ecosystem? And so the question of - maybe we just "plant" more collembola - isn't really the question we need to ask, it's how do we create a healthy soil that supports an appropriate biodiverse range of life.

I recently asked the question of whether we should really be paying for non-indigenous microbes when we have a perfectly good indigenous microbes right in our backyards. There are benefits to both I believe and yet for some reason I'm stuck thinking that indigenous microbes are better adapted to our local environments, soils, and soil food webs. We know for example that parasitic nematodes are great, but they don't all survive in northern climates (e.g., S. riobrava). However, I am also aware the nature is pretty adaptable. Then I remembered the term 'pleomorphism' from the Microbiology 101 days. In microbiology, pleomorphism is the ability of some micro-organisms to alter their morphology, biological functions, or reproductive modes in response to environmental conditions. Meaning that life is adaptable. Some life adapts more quickly, other not so much. But organisms like bacteria and fungi with relatively short life cycles can be presumed to quickly adapt to whatever new environment they get thrown into. But, the question of whether all manufactured microbes are equally pleomorphic or not - or can even become as adapted as indigenous microbes - the simple take-away is that the more individual strands of the soil food web that we can encourage and support the better. And that nature usually provides all that it needs.

Would transplanting some partially decomposed and infected AO leaves into an orchard setting provide the necessary microarthropod component needed to to see the soil in perpetuity? Maybe just interplanting AO (or along the orchard perimeter) with trees will provide enough leaf litter to support the higher levels of collembola. We do know that AO provides numerous other benefits to an orchard environment, like nitrogen fixing. And its invasive "properties" not withstanding, AO could be the perfect orchard understory bush (help me permaculturists - a Level 3 mid-story canopy plant?) that fixes nitrogen, feed the birds, provides edible and ciderable fruit, encourages soil biodiversity, etc.

This year Jason and I made an apple cider blend with AO fruit. The fermentation (all wild) was the most vigorous and cleanest of all the blends. It seems there is something magically clean and alive about AO that benefits many levels of life. I do have some other materials (thanks again Eliza) that I plan on reading that deeper into this study she referenced. So hopefully more to come on all of this.

Mike Biltonen, Know Your Roots
Zone 5b in New York

Edited 1 time(s). Last edit at 03/14/2020 02:21PM by Mike Biltonen.
Re: Microarthropod grazers?
March 14, 2020 02:31PM
Funny that we both commented on leaf litter and fermentation at about the same time.
I believe all life are generalists when it comes to feeding - within reason. Almost no organisms benefit from a singular diet. That I know of anyway. Specific associations for sure, but not a singular diet. I suspect the collembola are benefits from the leaf litter as food source, immune boosting fungi, and the secondary metabolites of the plant's induced/systemic resistance processes, which is why the literature illustrates them eating more than just the fungal bodies or individual parts. Again, it all speaks to biodiversity and healthy vibrant support systems in our orchard. And planting lots of AO!!

Mike Biltonen, Know Your Roots
Zone 5b in New York
Re: Microarthropod grazers?
March 14, 2020 04:02PM
Before I head off to work, I also wanted to give some background of how this study in walnut anthracnose and AO came about. It was widely known back in the 70s (I think that was the era) that companion planting AO with black walnut increased the height and diameter of the walnut trees for timber production. This practice was abandoned due to the invasive nature of AO when it isnt managed. The plant, not the lack of management, got the blame.

And then they noticed that these walnut trees looked great, in addition to being larger in every way.... and that's how this study came about.
Re: Microarthropod grazers?
March 15, 2020 05:28PM
Thanks Eliza, very interesting!
In one article I found, it seems as though AO was planted quite densely, two for each black walnut on a close 1.2 x 2.4m spacing. We can't do that easily in our apple orchard, but can imagine lightly introducing AO. Seems like it will interfere with mowing under/around our semidwarfs. Coppicing once a year might work, but not multiple mowings. This may be a situation where adding some AO to a high density planting might be easier than to one with larger trees.

Hemlock Grove Farm
Zone 5 in New York
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