Alternaria

In West Coast Nuts' September 18th article, Cecilia Parsons reports on research by UC plant pathologist Themis Michailidis into the fungi involved and how they reach the kernel.

Michailidis' research links most walnut mold to Fusarium and Alternaria.

But where Botryosphaeria canker and blight are prevalent, that fungus can become the leading cause.

Hull damage from walnut blight, sunburn, or insects gives mold fungi a root inside.

Okay.

But the Alternaria, Aspergillus, You know, all these things that everyone knows are the late season blights.

They literally were in there to begin with.

And you'll find all these papers being like, oh, there's a healthy plant with

Alternaria inside of it.

And then they credit that there's the right minerals or there's the right endophyte that's retasking it.

So, and realistically, it's got a balance of microbes, but it's giving it the sugar and it's not allowing it to take over the whole plant because there's other microbes there.

Obviously, if we treated our soil with biocontrol, which is what that is, we will make it so that that role, the endophytic role that the Aspergillus fumigatus, that the Alternaria, that all these pathogens that everyone's really worried about, we just occupy that role.

So yeah, it's another fungal leaf spot.

So if I'm going to just manage this with conventional fungicides, the conventional fungicides would be the same for Alternaria as they would for Stemphylium.

That is one of those cases where there's some overlap.

But if I have a major problem with that, maybe I want to consider one of those hybrid tomato varieties that does have resistance to it.

So potentially we could manage that.

But on top of that, you've got Alternaria.

which is a stubble-borne disease, once again, we don't have any genetics to that.

The only control for that is fungicides.

And that's fine, except the majority of the yield loss that's associated with Alternaria is pod infection.

And we're talking 20% to 50% yield loss we've measured with Alternaria.

And you can't put a fungicide on your pods because of MRL issues.

So if you increase your Alternaria risk, you are in serious trouble.

There was nothing exotic about them.

I isolated Penicillium genera and Alternaria genera, and you find them on agricultural stuff all the time.

So there's nothing really surprising that I saw those fungi, and I, I did that identification by doing, uh, ITS, uh, gene sequencing.

I was a little disappointed that I didn't find a higher diversity of microbes in my culture collection.

With nary a worry in their head.

So that right there is likely Alternaria.

Okay.

And it's brown and it has thick hyphae, as you'll see in a second.

Like, huh? Uh-oh.

Which fungi is which? Right.

The top right one looks a lot like Alternaria and has that thick brown hyphae.

So my friends and Dr. James White would all beg to differ that, sir, that you can't tell plant pathogenic from the beneficial.