Hi Greg, I remember trying to find that info also and was not able to.

I’m in San Diego and every farm I know of is struggling with PM worse than normal. Our farm used to have terrible problems with it, but now it’s quite minimal. Over the last year we did extensive trials to figure out the conditions that shift the relationship between the plant and PM to “malignant”… Yes, I now believe it’s not a disease, but actually a friend of the plant…though not always a friend to our profits. But, with some understanding of their relationship, you can help them both out so that everyone gets more out of it, including the farmer.

Everyone is getting PM in SoCal now because we haven’t gotten any rain and our irrigation/soil has high levels of sodium chloride. We depend on rain to flush the sodium chloride out of the soil, but even in a good year of rain, it’s still not enough. Most folks I know are using calcium sulfate, potassium sulfate and magnesium sulfate to displace the sodium chloride toxicity, but this is a mistake. The sulfate(SO4) puts a lot of oxygen in the soil, and when the plant takes it up, the plant has to do a lot of work to reduce the sulfate. Moreover, the plant needs less sulfur than nitrogen or carbon, so the plant will always prioritize spending it’s energy on reducing NO3, CO2, CO3, before SO4….which creates a pile up of SO4 in the plant that creates even more work for the plant to take up K2SO4, CaSO4, MgSO4.

Secondly, generally farms never irrigate as much as the rain does, so when we’ve gone without rain for so long, the soil becomes more and more oxidized, from being dry and from less accumulation of photosynthesis.

I believe plant and PM symbiotically co-evolved. PM is not inherently pathogenic. They have a pact: when the plant can’t mantain a suficient redox state (becomes too oxidized) it will signal to the fungi, to take over the plant and decompose it’s body to make nutrients available for the next life cycle. The fungi was there the whole time and helping the plant maintain it’s reduced state, until the plant just couldn’t keep up with oxidation pressure. The plant thanks the fungi…”since you’ve been helping me my whole life, when I start to decline I’ll give you first dibs on my body” I could write a couple more pages on this alone, but I’ll leave it there. The takeaway, is that you have to keep the plant in it’s prime so that it doesn’t prematurely tell the fungi to take over…but eventually the PM will start the decomposition cycle and that’s not a bad thing.

Here’s how you keep the relationships good:

If you’re adding sulfates, stop adding sulfates. However the plant still has to do work to shuffle the sodium and chloride around and try to keep it out of the plant.

The solution to this problem is providing C, K, Ca, Mg in a slightly* reduced state(with a little energy). The simplest cheapest method is foliars and fertigation with a combo of Calcium Acetate Ca(CH3COO)2, Magnesium Acetate Mg(CH3COO)2 and Potassium Bicarbonate* KHCO3. These will provide the cations needed to displace the sodium toxicity and the carbon + energy to displace the chloride. You can make Ca Acetate cheaply by mixing vinegar with limestone and and Mg Acetate by mixing vinegar with dolomitic limestone. Potassium bicarbonate is organically available in ash. I like Seven Springs’ Sunflower Ash. I can give precise recipes if you like.

*Q: Why did I write “slightly” reduced state and not a very reduced state? Why use potassium bicarbonate and not potassium acetate? If the plant wants reduction, why not use only reduced nutrients?

A: When you are adding reduction energy to the ecosystem, the plants can use that energy, but so can countless other microbes. If you dump a lot of acetates on your ecosystem, a bacteria that likes acetates will start stealing a lot of it, and when they eat it, they will poop it out as CaCO3 and MgCO3 which are not soluble unless they come in contact with an acid, in which case they will raise the pH of your soil solution, which is not good.

So Ca Acetate and Mg Acetate are great fertilizers, but they are combustible fuel for the fire, so you need to apply them in very low doses so that you don’t disrupt the energy relationships (including pH) of the soil (disrupting the stability of the soil ecosystem). This is why you can deliver more nutrients per application if you mix in potassium bicarbonate with a Ca Acetate and Mg Acetate solution. Potassium bicarbonate is soluble and has no energy, which means only the plants can use it. KHCO3 will lower the total energy density of the K/Ca/Mg solution.

I don’t know about Artemesia, but in your particular context, I would be searching for ground cover that is halophilic or salt tolerant, so that every inch of your farm is photosynthesizing efficiently, pumping energy in the soil, regardless how much rain you get. It’s pretty damn hard to reduce sodium chloride in the soil in a way that actually improves plant health. I believe the better strategy long term is to improve the energy and stability of the soil, so that the plants are more resourced to manage the salt.
If artemesia is working it’s because it’s helping increase the energy of the soil and stability of that energy in the soil. And I would guess it does that well under certain contexts. And possibly it’s photosynthetic efficiency is well matched to feed the soil when the vines really need it.

We also just installed an industrial RO system on our farm to reduce the sodium chloride in our irrigation. It’s expensive though…