Open Integrated Pest Management Education Resource

Getting to the Root of the Issue: Field Diagnosis of Root Diseases 10/03/2019




Field Diagnosis of Root Diseases

Swain:

[00:00:12]

We all have situations where we've got something dying in the landscape and we've kind of puzzled as to what might be causing it. And this technique that we're going to talk about here, it's probably nothing new to most of you, is basically how we're going to figure this thing out. Most plants, as we have either root disease from over watering, root loss from various different sources, be it gophers or construction, or simply lack of water, Show drought symptoms when they're under stress. So, the way we figure this out is we start looking at if the whole plant begins declining altogether, overall, we're seeing similar symptoms from branch to branch, that sort of thing, or the symptoms are restricted to the south or southwest side; that's a good sign that we've got a water problem. But water problems are related to root problems. And so, we're going to talk about how to try and disentangle some of this stuff.


Swain:

[00:01:25]

Okay. So, you know, half the time when I get these kinds of questions, people bring stuff in. And this is an actual sample that somebody brought in. You know, it's like, "Okay, I have this dying twig. What's wrong with my plant?" And it's a little challenging to diagnose from that. But as I mentioned, there are a host of different things that we could be looking at, everything from over watering and root disease, drowning in clay soil. Certain plants especially do not have to actually have a root disease like a Phytophthora or a malaria to have their roots simply stop functioning when they're in too much water.


Swain:

[00:02:05]

Roots for most plants require oxygen. And if they sit in water for months at a time and compacted clay soils, they will drown. And then, you know, that kills them. And that's pretty much the same as if a gopher clipped it off or somebody comes in with a backhoe or parks a car on it all the time.


Swain:

[00:02:25]

So here's some examples. This is Box. I believe this was Court of Madeira, and, you know, you're looking at this and you're kind of going, huh? Least one of these plants doesn't look good. Actually, maybe the middle and the left don't look good. The only one that looks okay is on the right, you know. So, what's going on here? It's a fairly new installation. So right over here. I don't know if it's showing up in the slide. You can see they've got a laser line there. So pretty clearly the plants should be getting water. The question is, you know, what's going wrong? We'll figure these things out as we go. I'm just bringing up examples, okay.


Swain:

[00:03:02]

So, then this is also sort of a classic case. We have a fruitless mulberry in Terra Linda. And it's not looking good. We've got a dead branch tips all the way out here. The whole trees yellowing. And what's going wrong with this? Versus, you know, here we have an Agave that is bubbling, and the leaves are dying. You can only barely see it here, but there's a bunch of exits eight coming from the base and we're wondering what's going on there. And you know what we're going to do to figure these things out is really essentially the same. So, we'll take a peek at some of this.


Swain:

[00:03:46]

Oh, and finally, we have a whole garden showing similar symptoms. We've got blackening. The new growth is dying here on roses. I don't even remember what plant species this is. I think it's something like verbena. But, you know, the plants declining fairly much overall. We have a few little spots that are making it.


Swain:

[00:04:09]

Okay, so we're going to do root crown inspections. That's the plan. And so, we should see the deficiencies distributed over the entire plant. And this includes water deficiency symptoms distributed over the entire plant. Even if we think that this is over watering. What we're really going to be looking for are symptoms near the root crown. So, we're going to be looking for when we do the inspection. So, we're going to look at the tree overall and we are going to see this and then we're going to home in on the base of the tree and we're going to look for things that look like this. So, this is a cherry tree, and these are not normal. This is bleeding. Almost everything in pruneness does this. I know you guys know. And so, we'll take a peek there or we're looking for other things like this. This is arbutus marina, strawberry tree, or arbutus unedo sometimes can look fairly similar. And you get this--so this is a canker. This was a canker, too, by the way. You just the canker is sort of hidden under there. You'll see it when we peel back the bark. And this you don't need to peel back the bark. You can pretty much trace the outline of a canker just looking right here. The vertical cracking is the wood drying out. And this eventually will start turning a darker color. You can see the dark beginning here as it creeps up the side of the tree.


[00:05:36]

Anybody seen any of this? Yeah, plenty. Good. So, if you guys see it and you feel like working with me a little bit on this, maybe we can cut some samples up and send them Suzanne Latham at CDFA. And if you have a moment. Yeah, do you have a question?


Participant:

[00:06:00]

Does arbutus marina have the same problem?


Swain:

[00:06:04]

So, yes. And it's rampant in the Bay Area right now. And we do not know what it is. We have some ideas. The problem is this.


Participant:

[00:06:18]

Inaudible


Swain:

[00:06:47]

I've seen one hang on in Santa Cruz for about five. But that's the exception, not the rule. I agree with you. Everything he said is accurate. I mean, so we're simpatico. Yeah. We are seeing the same thing.


Participant:

[00:07:14]

Inaudible.


Swain:

[00:07:14]

Yeah, and we haven't given you an answer yet. I'm so sorry. Right. Exactly. So, arbutus marinas, if you guys want to let me know, I'll see if I can come down and pick it up or something. I cut him up and send him in to CDFA. The best success we're having right now is trying to isolate from the root balls. When I say best success, the problem is this. You've got it. I'll make an analogy. You got a dead cow in the field, right. You see a vulture on the cow. Oh, well, vultures must be killing the cow because every time a dead cow I see I got a vulture on. It's not necessarily true. Well, we have the same problem with this. We try isolating from the root ball of this and we get something back consistently. Just because we get something back off a dying root ball consistently does not mean it's killing the plant. That means then we have to take that thing and find a healthy arbutus marina, put it in a pot and greenhouse, inoculate it and see if we can get the same symptoms. If it's capable of killing a healthy tree, then we might have the pathogen. But, you know, there's a lot of things living on these root balls. And a bunch of them are not killers. They're just decay organisms, agents. Okay, one of those two words. I conflated them. Yeah. Question.


Participant:

[00:08:44]

Is it the same for phyra?


Swain:

[00:08:44]

We have seen it show up two or three feet above the base of the tree. Because when you cut these in sections, this is coming up through the middle of the tree. So, I don't know if you guys are familiar with eutypa or neofusicoccum, or maybe, you know it as dead arm in grapes. But this stuff is going up. We believe it's attacking through the base of the tree. And it looks like it's coming up through the core of the tree, and then it's working its way out. So that's why you see it dying here. I'll just do this. You see it dying. It's killed this section and the tree--you can see this faint little bulge where it's trying to grow over the outside of the thing and it's trying to, compartmentalize the decay--you guys all know shigo compartmentalization of decay trees--and grow over it. Unfortunately, what will happen is in the next couple of years, it will break that inner barrier on the inside of the tree and punch through to all that new wood and kill that, too. And it takes several years for it for this to occur but that's why it decays. Anyway, we're getting off topic.


Participant:

[00:09:54]

Is this possible another picture of phytophthora?


Swain:

[00:10:00]

No, I do. I mean, that's a good question. We thought the same thing. But phytophthoras tend to work on the outside of the tree and kill the living tissue. And they do not work from the inside. That's why we think it's one of these buttress farian neofusicoccum one of these deep wood decay agents, sorry, pathogens that's working its way out.


Swain:

[00:10:27]

Okay, so this is what we're trying to figure out. These are the kinds of things that we're using this technique for. So, if we have acute drought, what are we going to see? We're going to see something like fresh growth wilting. We're going to see harden growth being less affected. We're going to see potentially some sunburn on the on the more mature leaves and the soil will be dry. And if we do a root crown inspection here, we should expect to find healthy roots. Because it's just acute drought, as opposed to chronic drought where the fresh growth will be stunted. Often, it's chlorotic and we can go into the ABCs of why that is plant physiology, but basically a plant that doesn't have water, can't do what? Yeah, provide nourishment, move minerals, all that other stuff, if it has no nourishment, if it has no sugars to build, it can't do things like build accessory pigments that help make the tree, not sunburn. So, it's basically running a deficit every year. Now, that's not going to happen on an annual plant. Annual plants don't run deficits every year because they're dead by the end of the first year. So chronic droughts only going to really happen on larger trees and those kinds of things. We'll go back to that in a little bit.


Swain:

[00:11:49]

But again, even in chronic drought, root crown inspections should reveal healthy roots in a perfect world. And this is what you're going to find. So, this is a sample from underneath that tree. Okay. The grass...this isn't rocket science. I mean, you guys are going to laugh and say, yeah, you need to run a soil sample on this. But I did it just to sort of say, look how crumbly and dry the soil is in the top inch or two of the soil. That tree has nothing to work with, right. And then I took another one from a tree nearby that looked comparatively healthier. And while the tree looked bad, but the lawn looked better. So, you're thinking it's getting water? Well, yeah, it's getting water in the top two inches and it's still crumbly and dry down below that. So, the trees getting nothing. So, you know, a soil probe is helpful when, you know, pay attention to the depth of the soil. Pay attention to the soil when you're excavating around the root of the tree.


Swain:

[00:12:49]

Now, once your flooding it can produce this same thing. So, I mean, what do you think is happening to the roots here? To the trees? Yeah, they're drowning. They're not getting any oxygen. And when, you know, roots need oxygen, just like anything else. Now, you'll find exceptions to this, you know, swamp cypress and some things like that. They have arankema. They can move air down into their roots so that they can breathe underwater, essentially.


Swain:

[00:13:16]

But what happens here is that the first roots to recover--Now, this this rancher, it's not really the best photo because this orchardist is flooding their field. This is flood irrigation. This is fine, right? Because the plant can take this for a couple of days. It's when it sits like this for weeks that we generally have problems. And even when it sits like this for weeks, eventually the water subsides, and which roots recover first? The surface roots because they're the ones that dry out first. So, the ones that typically die when we have winter flooding problems in clay soils, flats with poor drainage, they're going to be the deep roots. Which means when summer comes around, the plant is left with surface roots only. And it can't chase the water as it goes down. So that's when you're going to start seeing either chronic or acute drought symptoms.


Swain:

[00:14:15]

So this is an example. This is a pittosporum that was planted in situations that were just discussing, flat clay pan that floods in the winter. This is what we found when we went through and started looking at the base of the tree. And you can see that something, that decay came up and got it. Now, this probably was a phytophthora based on what it looks like here.


[00:14:44]

But it's a little bit. You guys remember the disease triangle, right? You've got to have the target organism. You've got to have the disease. You got to have the environmental conditions that are right. Arguing about whether this was environmental conditions or phytophthora is a little bit of a chicken or the egg kind of argument because the phytophthora survives in the right environmental conditions. So, now we're getting to this problem of attribution. And what do you tell a client? You know, what do we have? Do we have a drainage problem, or do we have a phytophthora problem?


Swain:

[00:15:17]

Right. Yes, you do. So, of course, we got construction. So, obviously we've lost a few roots here. And this is going to be a problem. That tree will probably look good next year and maybe not so much after that. And that's because the tree itself is a massive storage system for energy. So, the symptoms of the impact here might not be seen for years. I mean, okay, this is a bit extreme. So, you might see symptoms next year. In more subtle cases, it'll will last a little longer.


Swain:

[00:15:53]

Shorter plants, you have a shorter timeline. And so, when we do a root crown inspection here and I'll get to what a root crown inspection is, you know, a little bit. It might show a pathogen. It might show root damage. But it really depends. You'll see the root damage here, for a root crown inspection. But if they did the trenching three or five feet out and you do a crown inspection right around the base of the tree, you're not going to see the root damage necessarily. So, this is a case where a good site history is going to be important. I know you guys know this. You're working your own. A lot of you manage your own landscapes. So, you're going to have a site history. But if you're a master gardener or if you're in the trades half the time, you're showing up for the first time and somebody called you after the plants, halfway down the slide and saying, "Hey, can we save this?" And you need to understand what's been happening in the last five to 10 years before you even got there. So, this is a case where we might want to really focus on our interview more than that.


Swain:

[00:16:50]

Compaction. This can be subtle. You know, it's really obvious when you've got a whole bunch of cars parked right underneath the tree. But again, you may not get called out, or you may not even know that people are parking cars on this particular site. When you get asked to figure out what's going on, and you know it, it seems obvious soil is going to be very hard and the water isn't going to move through what's effectively concrete very well. And again, this is not going to be a problem for annuals because they're just not going to want to grow in something that's this hard. You'll get weeds. And that's about it. But nobody's calling you out usually to figure out what the problem is with weeds. They're calling you because they're trying to figure out what the problem is with usually fairly valuable landscape trees. I'm surprised at how many times gophers are a problem in urban areas. I live in Petaluma. We have sandy loams. Gophers do the backstroke through it, but it's sort of the country. So, you expect it, but not always in, you know, downtown areas. And sometimes when I do my root crown inspection, I'll begin digging down and I'll try and go and there'll be nothing but air underneath the trees. Why is that? I mean, you're like, "Okay, well, because gophers dig holes." But gophers like digging holes underneath plants and underneath water lines and underneath other things like that because they are a root system for them. You know, those root systems hold the soil in place, so it doesn't collapse on them. So, a shrub is a perfect place to dig underneath. But unfortunately, if you get the intersection of three or four gopher runs underneath that plant, there's a lot of air there. And the gophers tend to get more desperate in drought and start looking for wet things to chew on. And you can have a lot of root loss. And all of these things will present. The reason I'm going through these is these all will present the same way on the outside.


Swain:

[00:18:58]

Grubs. So, this is mostly beetle larvae and we see it on agave. We do see it on a few other things thuya and other moist conifers, (Inaudible) separate those kinds of things. We have strawberry root weevils. We have black vine root weevils and. But I'm going to focus a little bit on what is becoming an increasing problem, the agave root weevil.


Swain:

[00:19:19]

So this has been in Sonoma and it tends to be where people import succulents from New Mexico and places like that. But you'll begin seeing these lower bracts. I'm not sure that's actually a bract, or not; these lower leaves die first. So, this is the agave root weevil. Other weevils are going to look somewhat similar. The strawberry root level does not have the classic weevil snout but it's a weevil, nonetheless. And this is what you're going to typically see. You're going to probably have to pull a couple of these plants because they're going to be so bad, your client is not going to mind and you're going to find some holes and damage like this. And if you're lucky, you'll find a head of one and the tail of another growing right out of these tunnels.


Swain:

[00:20:11]

You’re not going to have enough root tissue here. They're going to be feeding on the smaller roots. So, when you do your root crown inspection, you're going to start digging around there. You're going to come up with these little tiny white C shaped grubs and there will be a profusion of them. And that's just telling you, you're losing all the tiny roots at the base of your conifer. So those are the kinds of things that would all produce these types of symptoms.


Swain:

[00:20:34]

So here we have a case, this was San Rafael, some place. The house was going on the market. They wanted curb appeal. So, they started watering the snot out of the landscape in the front. Obviously, they're on a slope. So, the plants at the top of the sloped look great. But all of a sudden, the plants at the bottom of the slope started dying. And the question was, what's going on? So, when we do a root crown inspection, what are the first things we're going to do? Who does root crown inspections in the field?


Swain:

[00:21:07]

Okay, so one of the people who raised your hand. Anybody want to volunteer what the first thing you're going to do it and root crown inspection? After looking at the overall plant. Yeah.


Participant:

[00:21:19]

Removing the leaves or whatever around the crown?


Swain:

[00:21:19]

Okay, good. And then how are you going to tell? Then tell me the next step after that.


Participant:

[00:21:31]

I look for damage or decay and then it depends after that.


Swain:

[00:21:35]

Good. Depends after that. So, what my next step is after I look for damage and decay, that's going to say where I want to end up sampling. I'm going to start slicing. I'm going to take these very thin slices, you know, disinfect your tools, that just go into the bark enough for me to see the color of the healthy bark. And I'm going to start fairly high on the plant. The problem is this. Most plants have fairly similar colored bark, but you can't be guaranteed of that. For instance, Coast Live Oak, the bark tissue on a healthy Coast Live Oak can be anything from burgundy to pale sherbet. And that's a pretty wide range. And if you slice in at the root crown and you find burgundy and you're used to looking at pale sherbet, you're going to think, I've found something that looks like root disease, but it's just the healthy tissue on the plant. So I usually start fairly high on the plant and take a nick into what I'm pretty sure is going to be healthy tissue, so I know what I'm trying to compare against as I work my way down. Does that make sense?


Swain:

[00:22:37]

So you can see evidence of this. So, on this particular juniper, we've got a pink color for healthy tissue here. And I've sliced a couple different places and let's go back for just a second. This is obviously dead. That is not the plant we're working with here. This is pretty healthy, and that's the color that we would expect a healthy juniper tissue to be. This is a little paler green. Can you see that? Is it showing up in the slide? That's the plant we're working with. This is already dead. It's unlikely to tell us all that much. We might figure it out. This is much more likely. So, this is the plant we're going to work with. And then we're starting high, working our way down. And the soil line was right about here on this particular plant. And as I worked my way down, we went from pink to pink to, ah, oh, this is the color to burgundy and white. So, we've got a problem.


Swain:

[00:23:38]

And we're not going to worry too much about what our problem is right now. But that white, then I went further down, cut another two inches, and just stuck my thumb in and peeled the tissue back and we have this plaque of white material. So, this is armillaria. And I'm not asking that you necessarily remember this stuff. Most of this stuff you can look up on, UCIPM. But I am going to bring up armillaria, phytophthora and one or two other things, because these are the 90 percent of the root problems you're going to run into are going to involve these if it's disease and it's not something. And even if it's construction damage and those kinds of things, when you damage the roots so badly and they have a hard time closing in time, you often end up with one of these things in the root systems.


Swain:

[00:24:26]

Armillaria. There's a number of different ways to diagnose it. It likes summer irrigation. It's a native pathogen. At least I believe it's native. It's been here for a really long time if it's not native. And it likes consistently warm, moist conditions. And so that means that it tends to thrive in hot summer situations where we irrigate, because California being summer dry, that those warm, moist conditions don't show up all that often. So, you're going to see it in vineyards and lawns and places like that. And it really likes injured roots, especially if somebody has removed a tree nearby and not pulled the roots out of that tree, because armillaria, unlike most of the other pathogens here, survives very well by breaking down. It can survive as a saprophyte. It can eat dead wood, essentially. And it can happily munch on dead wood for decades. In the cases of some of these orchards.


Swain:

[00:25:27]

So, really quickly diverge a little bit here. How did you make money in California in 1849, 1850? Yeah. That's how you made money in California in 1850. You sold denim. I mean everybody usually says you go look for gold. Whiskey also, right. The guys who went out and looked for gold, if they found it usually came in, bought a pair of blue jeans, blew a bunch of money on whiskey, and sooner or later they didn't have any gold. The way you really made money in California was you sold fruit, you sold denim, you sold whiskey. So, the people who made a lot of money in California happened to be orchardists. And you guys might remember San Jose, they had a lot of nice orchards in it once upon a time, I mean, you don't remember having seen it. I don't think anybody here is quite that old. You are?


Participant:

[00:26:29]

(Inaudible)


Swain:

[00:26:32]

Right. Exactly. We can still remember that some of those old orchards existed at least until fairly recently. So, what did they do when they got here? Those orchards weren't here in 1830. So, if you were an orchardist, you went out and you cut down what? Huge oaks that were the landmark, you know, that's why they called Oakland, Oakland, right, because they had these, you know, oaks that were three, four or five feet around, across at the base. And did you pull those five-foot stumps? Too much work. You could try and burn them. Half the time there would be re-sprouting, they did not want to burn, so you left him in place half the time you planted your orchards around them. And then what happened? Well, you produce good fruit out of that orchard for about 20 years. But armillaria was in there eating those dead root stumps. Right. And when the dead roots stumps sort of, when it had finished eating all of them, it took a long time because a five-foot oak has a big root system. So about 20 years in, in the 1870's, 1880's the armillaria ran out of oaks, and it had grown big and fat and mean in the meantime.


Swain:

[00:27:55]

And what did it go for after that? The only thing that was left, all the people’s orchards. So in the 1880's and 1890's, a bunch of people who had been sending their kids to college, making a good living running orchards in the San Jose area went belly up because our armillaria ate their orchards, because it simply grew out from those dead oak roots dumps and went out and attacked the orchards and it was pretty much unstoppable. You guys ever hear the humongous fungus?


Swain:

[00:28:31]

Yeah, it's an arm malaria infection that's several miles wide and we talk about it like it's one, but there's one up in northeastern Oregon, there's another in Idaho, I guess there's another one in Michigan. They didn't even realize this was the same thing until they flew over the area and saw this huge ring of trees three miles wide. That's n armillaria infection. So, it's a pretty serious thing. Once it gets established, it can overwhelm a host’s defenses of even fairly healthy trees. So, I'm just talking about--this is useful for me anyway, from remembering all this kind of stuff to remember how armillaria works. And if you've got a dead root stump someplace and you've got a tree declining near it, that'd be one of your big clues that you should probably be looking for some of these symptoms.


Swain:

[00:29:14]

Okay, so here we have an orange tree. It was in a terrace in San Rafael. And this orange tree, the new person bought the house, saw that the soil in the terraces was about eight, 10 inches below the edges of the walls that formed the terrace and they decided that their orange trees there, had needed more soil to really be happy. So, they brought in about six inches of topsoil and put it all around their orange trees and then could not figure out the next year why the orange trees were performing so poorly. So, we went out and we did the root crown inspection. So, we did just like the gentleman over here was telling us about. We cleared away all this stuff and looked for bad things at the base of the tree, bleeding spots, cankers, things like that. Didn't find anything. But what we didn't notice is the tree, instead of having a nice root flare where it went into the ground, just went straight down. And then we're like, "Hey, does this doesn't look right." You know, we started asking, what's gone on? Can you tell me the history? Oh, yeah. I put six inches of topsoil on this. It's like, oh, oh. So, then we started digging around the base of the tree. And I made a little cut high on the tree. And I worked my way down. And then I had to start digging and work my way down farther and farther until I found the root crown of the tree. And just about where I found the root crown of the tree--so, the color of this tree's bark when you slice into it, is this sort of creamy, almost butter-yellow, but maybe buff, you know, somewhere in there. It's not quite as rich in this picture as it normally would have been. And about four inches down, I ran the color change from this buff, cream color that. And then just below that, I could stick my thumb into the bark and just peel it off. And when I peeled it off, I got this. Can you see the difference in the color here? This is a cold white and that's sort of a warm white. And that's our malaria coming up through the base of the tree. So, we were able to figure that out.


Swain:

[00:31:21]

The other thing that I like to use is--sometimes it doesn't show great symptoms like this--so, your sense of smell is useful. If you can find a fairly rich, fresh infestation. It will smell like fresh mushrooms. It'll smell tasty. Yeah, a question?


Participant:

[00:31:46]

(Inaudible)


Swain:

[00:31:46]

Absolutely. Although it's not great eating, right? I mean, you'd think it'd be nice if it's got the name honey mushroom, right. Sometimes you get clumps of tan mushrooms. We saw that in this here, with white spores coming up. But they come up about starting about now. After the first rains, you'll start seeing these guys come up. But you can't use them reliably because if you're trying to do this in June, then you're not going to find anything. The problem is this. It doesn't always show these big white mycelium mats. So, this is trachelospermum jasminoides, so star jasmine. And this is an area with some very healthy mayaporum, no sorry. It starts with an M. matan trees, sorry.


Swain:

[00:32:42]

Had some healthy matan trees growing around it and some redwoods farther away, and all of the star jasmine died here. And we could not figure out why. And I actually had a hard time, too, because when I was stripping these things out, I would take the knife and start peeling the bark off of these things. I was getting nothing, really. This is the closest. That's the best I got right there. And you will see a little streak of white in there. But one of the problems was-- and this is the best I found. So, I spent like two hours looking out there. And most of the stuff looked like this. It was just dead and hard and gone. And then I found one root section that had a few patches of white. And I started saying, "Oh, now I think I know what's going on." And then as soon as I found that, I started looking at the bark that I had been peeling off. I was looking at the root and I had not been looking at the bark and most of the armillaria for these sticks in the bark. It does not stay on the root. So, when you peel the bark off and then you look at the root, you're missing what you should be looking at. So, if you're trying to do star jasmine with armillaria on it, it's going to be challenging, but it can't be done, you're just going to have to spend some time. And the funny thing is, you know, they talk about armillaria resistant plants and, you know, that's a little bit like deer resistant plants. They're going to go for what they can get. But, you know, the matan trees out here still looked great. Maybe they should handle root loss really well.


Swain:

[00:34:10]

So how do we manage it? I'm not going to spend a whole bunch more time on management. There are fungicides out there with armillaria on their label, including some that are fairly environmentally friendly, bio fungicide, that kind of thing. I'm thinking of tracederman might be on that. I'm thinking of...I'm not remembering it right now, streptomycin lydicous. I don't want to use trade names because I'm going to get in trouble. But I challenged the people who had it-- because I met him at one of these conferences and I said, "you guys have armillaria on your label. I know it doesn't work. You must know it doesn't work. Why is it on your label?" And they basically said because we got bought out by another company and they said, do you have any results that supports it on armillaria? And we said, well, yeah, in the lab only, you know, we know it doesn't work in the field. And they're like, put it on the label. And so, can't trust the labels on some of this stuff because even though they know it doesn't work, you know, the reps know it doesn't work. They want to argue with you. But the higher ups have deemed that it will happen.


Swain:

[00:35:27]

So, armillaria management is mostly about managing water. So, if, like we said, armillaria likes things moist and warm in the summer, so we're going to try and let soils dry out pretty thoroughly between watering. Now, that can get really challenging on clay soils, but it's what has to be done. There are no chemistries that have been shown to be effective despite what's on the labels except things that are already being banned, things like methyl bromide and those kinds of things, which would have killed your trees anyway. So, your options are really removing the trees or air spading. Air spading can work. It will not revive that dead root. It doesn't have a dead root in this picture. But if that was a dead root, it will not revive that dead root. But if you can dry things out and air spade it enough, it can help the trees stop incipient infections from getting much worse. So, it can be worth a try as a therapeutic treatment on very minor league infected trees. The guys who do most of this work have been in pear orchards. And the big advantage here is that it can keep it from moving from this tree to other trees, because as we've remembered, our armillaria moves from one plant to another plant using a mycelia highway. So, the mycelia grow through the soil and it transfers the nutrients from the dead stump and then uses those nutrients to overwhelm host defenses elsewhere. So, if you can break up that highway and keep it from transferring nutrients, you can keep this from spreading. Yeah?


Participant:

[00:37:05]

What is air spading?


Swain:

[00:37:07]

So air spading involves, perhaps you've seen these guys with these big trailers drawn air compressors. So, they've got a generator, a big air compressor. It's usually towed behind a truck and you are taking a giant hose and this part is solid and you have to wear goggles and you generally want, despite this picture right here, you usually want to have some big plywood barriers around and you are blowing the soil out from underneath the tree to a depth of about six, eight inches. And this technique preserves roots of about, you know, all the way down to about an eighth of an inch in diameter, which is pretty good. I mean, let's not pretend you're not doing damage to this. You are damaging this tree. It's a bit like stripping every leaf off the tree because you're stripping every root hair off of this thing when you're doing this. But it's not as bad as doing nothing and letting your armillaria come back in. So, it's a fairly effective technique. It's not cheap, it's not quiet, but it can stop movement of infections and it may stop trees that are infected, if the damage isn't too bad. Or, I guess I should say this, it may allow the tree to stop the infection. You're not doing much other than changing the environment so that it's not favorable to armillaria. If the tree is not too far gone, it's not going to stop. I saw a hand.


Participant:

[00:38:54]

(Inaudible)


Swain:

[00:38:54]

It puts them at risk, but like we said, armillaria is, if not native, then long-established pathogen in California. So, in the winter, there are spores everywhere. They are blowing in the wind. So, worrying about the spores, yes. The mushrooms probably are a source of infection. It is probably not helpful to have them really close to your trees. But let's not pretend that removing those mushrooms is going to take trees that were vulnerable and make them less vulnerable. If your tree is vulnerable, armillaria will find them eventually. So, I would not say that mushroom--I know this wasn't necessarily a question--those mushrooms are not a great risk. It's a little bit like worrying about phytoptheramora in Marin county. The bottom line is, if you have a tree that's susceptible to it, the Phytophthora is going to find it because there are so many spores, under the right conditions moving around. Does that make sense? Okay. I go back here and then I'll get to you.


Participant:

[00:40:12]

(Inaudible)


Swain:

[00:40:12]

Well, that's a little bit like Chris' trichoderma questions, so trichoderma has usually been touted as something that that can reduce fungal populations, or I don't think for a lot of these bio fungicides, we don't really know how they work, whether they are displacing things or competing with them or actually preying on them. All we know generally is when we get these fungal populations or bacterial populations established, disease incidence goes down. Usually it's about transmission. Most of these things do not cure the tree that you're applying to. So, as of now, we have not heard any really solidly good effects by any bio fungicide against armillaria, including trichoderma, does not work reliably enough to make it worth the effort of applying. Yes, a question?


Swain:

[00:41:11]

But here's one of the problems with any of the bio fungicides, is that they're living things. So, if we have a problem, I'm going to be glib again, forgive me, if we have a problem with antelope in Africa, right. And there's just too many and they're destroying the thing. We can air drop cheetahs in there and hope that they establish. But cheetahs are really not adapted, being air dropped out of helicopters. And I'm being glib like this because trichoderma and a lot of these bacteria products, they're not adapted sitting in a box on a shelf. You know what I mean? And when you apply them, if conditions aren't fairly right, it's going to be traumatic for them being introduced to a whole new environment. And if conditions aren't really right, they never get established. And if they never get established, they're not going to give you control. So, we have seen certain bio fungicides work really well under certain conditions. The problem is getting those conditions right every time is tricky and sometimes, we don't know why they don't establish.


Swain:

[00:42:17]

And that means and your application and your time costs money and a lot of clients aren't going to want to hear, particularly farmers who've got a million dollars in crop in the field aren't going to want to hear, "Oh, well, we tried. You know, we had a 30 percent potential success rate." You know, and they're like, "If I've got to pay for the time and money to apply, I don't want 30 percent. I want 90 percent at least." Otherwise, it doesn't make it cost effective. Anyway, we'll keep moving. Yeah?


Chris:

[00:42:57]

Are you distinguishing when you say that it's not effective for armillaria, are you talking about just curative or also preventive?


Swain:

[00:43:05]

Were saying definitely for curative and also potentially preventive. One of the things that Armillaria does is it's got these rhizomorphs, so it will be produced essentially root structures. They're not roots, they are fungal hyphae, but they grow like roots. They are armored like roots have bark on them. There are armored structures that can move through the soil and hunt for other susceptible plants. That's not like phytophthora. Phytophthoras swim in the soil. There are these delicate little zoospores and they're easy to eat. These armored structures that armillaria produces, it's a little bit like, you know, standing with your pitchforks against the cavalry charge and hoping you're going to be able to stop it. You know, yeah, you might do a little too slow it, but your things are looking dangerous for you.


Participant:

[00:44:00]

(Inaudible)


Swain:

[00:44:00]

No. You know, that's the surprising thing for armillaria. They don't, you know, the guys who've been successful at controlling spread, they do not remove the soil. They simply air spade it, dry it out, fluff it up, break the armillaria into a million tiny little fragments and then let the soil dry a bit and then they shovel it right back on. And what you're doing essentially is taking a tiger and turning it into a thousand little kittens. And it's not so hard to knock it back, you know. Success has been done without trucking off a whole bunch of soil. The problem also is, you know, better the devil you know than the devil you don't. If you're removing this soil, that means you have to bring soil in from someplace else. And one of the big problems is recently, at least in Marin County, has been clopyralid contamination from people using herbicides that control thistle's on ranchlands and yada, yada, yada.


Swain:

[00:44:54]

If you take out the armillaria and you bring in clopyralid contaminated soil, you've just traded one problem for another. So, I don't know what to tell you, but I don't think moving soil is really our best option for most of these.


Swain:

[00:45:10]

Okay, so that's armillaria, sort of in a nutshell. Phytophthora is one of the other really big things that we're going to run. And Chris, can you keep... Do we know how we're doing on time?


Chris:

[00:45:21]

We're fine.


Swain:

[00:45:21]

Okay. So, phytophthora is one of the other big things you're going to find in soils. So, I'm only bringing up a few of these things because these are the harder things to diagnose. Gophers are fairly self-evident. Construction damage is fairly self-evident. And I don't have a lot of great advice on how to fix construction damage. And generally speaking, you guys probably know gopher control at least as well as I do. You know, it comes down to trapping if you can. And if you can't, you're going to go to some other kind of, you know, poison type options or you're going to use exploding... Yes. Which I doubt anybody's doing in San Francisco. It's CO2. Yeah. So that's another poison option.


Participant:

[00:46:15]

(Inaudible)


Swain:

[00:46:15]

You don't. Okay, there you go. I know one guy was relatively successful using the map gas and igniting it. And, you know, and that worked really well. But it breaks waterlines. So, because gophers make their runs under water lines because it's a roof, right.


Chris:

[00:46:40]

(Inaudible)


Swain:

[00:46:42]

That's true. Okay, so I want to bring up phytophthora. It's the other big thing. Again, this is going to be warm, moist soil. So, again, we tend to see an uptick in this in drought years, perversely, because people irrigate in drought years more than they irrigated otherwise. So, we get more phytophthora and armillaria infections shortly after we've gone through a drought. So, the problem with talking about phytophthora, unlike armillaria, which is, you know, there are several different species, but we can talk fairly safely about them all about the same, because they all behave about the same. Phytophthoras aren't so simple. They're aerial phytophthoras and there are soil phytophthoras and they are warm season phytophthoras and there are cool season phytophthoras. So, I do want to make it, too. We're not going to dive too far into this. Suffice it to say that if you've got a soil borne phytophthora, it usually works its way up. And this is a walnut. So walnut, again, I started higher. You can't see where I cut in high. I thought I was starting higher. I only took one slightly higher sample on one side of this tree.


Swain:

[00:47:49]

The color of the healthy tissue is sort of an orange gold. It's showing up very yellow in this slide. And you will not find any fungal structures in this, n white mycelial mats, because phytophthoras are all microscopic, or functionally microscopic. And most of these are primary pathogens. A lot of plants don't have inherent resistance to them. They all require free water to infect. So that's why irrigation systems--it's not just necessarily moist soil--they have to have water that's free enough to begin to flow. So, they tend to thrive in these drench and drought irrigation regimes.


Swain:

[00:48:39]

And this is something that, you know, we've been promoting a little bit. I mean, I have anyway, I've been saying, "Okay, what do you do about your plants in drought situations?" Water them thoroughly and then let the soil dry. The problem is you need to get to know your plants and how much is thoroughly enough and how dry is dry enough. When do you have to? And if you get this wrong, phytophthoras are going to be your enemies.


Participant:

[00:49:05]

Any suggestions on that? I mean, one thing that we've been looking at, I've managed some irrigation at Presidio, and for the forestry projects we've been working with a water system that replicates rain events. So normally around here, we get a big storm that goes through maybe a couple of inches. Everything is soaked for many, many days, a week or so, and then there'll be a month between the next rain. If we replicate irrigation that way, it's a natural cycle. It gets a clean soak and then you really dry out between storms. That's major and that's what we were thinking of doing, as we better plant results that way.


Swain:

[00:49:56]

Yeah, and I'm not going to tell you anything you don't already know, but that's not going to work for Japanese maple, because Japanese maple is not adapted to these sort of really dry cycles. Japanese maple likes things fairly consistently moist. So now you can do a little bit of drought and drench with Japanese maple. But what Japanese maple is going to think of as drought and drench is it's going to want, you know, an inch or two of irrigation once a week because it'll dry out in California in that amount of time. And I'm just throwing numbers out there because that all depends, as you know, on your soils. If you've got sandy soils, you're going to have to water a Japanese maple multiple times a week to keep it from burning and looking horrible, especially if it's got any kind of exposure. But on clay soils, you could get away with once a week because it holds onto water so well. So that technique will work brilliantly for most California natives, which is probably mostly what you're working with anyway. So that should work. But again, are we talking willows or are we talking Blue Oak because they're both trees. But Blue Oak pretty much can survive all summer long without anything. If you can get it to grow in San Francisco, which you probably can't because a powdery mildew. But you know what I'm saying.


Participant:

[00:51:15]

(Inaudible)


Swain:

[00:51:15]

Yes, you do. And that's all I'm trying to you know, we already covered that there are soil and aerial forms and warm versus cold weather. We have 200 species of phytophthora. More are being discovered every year. And your species probably matters when you're doing this. So just saying it's phytophthora isn't necessarily enough. If it's phytophthora cinnamomi, or phytophthora cactorum, it likes warm, moist soils. If you're dealing with...they're both soil borne. If you're dealing with phytophthora lateralis, it likes cool, wet soils. And it kind of shuts down in the summer. So that makes a huge difference on how you're trying to manage this if you're changing your irrigation regime to fit this thing. If you're dealing with sudden oak death, it's not even a soil borne pathogen. So even though it's a phytophthora, if you've got plants dying from that, you're not even worried about your irrigation regime. It's off the boards because it's an aerial phytophthora. Is this sort of making sense?


Swain:

[00:52:21]

Okay. But all require water to infect. So, this is an example, just really quickly, of how we do a root crown inspection. These are two things that are coming up from about three inches above grade. This is on prunus lusitanica which is Portuguese laurel. And you're getting these globs. Now globs, as you guys all know, are a standard defensive response of anything that's in rosacea. Essentially, you know, your prunes do it, your apples do it, your Portuguese laurels do it, all that stuff. So, this doesn't tell you have a disease necessarily you might have an insect boring in there. Somebody might have hit it with a stroller really hard or crashed a mountain bike into it and now it's just bleeding as a defensive response.


Swain:

[00:53:11]

So we slice in. The health color of the healthy tissue is this pale green. And then we find this hard, line here. That's typical. Not always the case. You also notice that where it was bleeding here, it's oozing out here. You'll see this little thing. I move the camera a little bit. Not my best work, but you get the idea.


Swain:

[00:53:36]

So and you'll find that the unlike armillaria, where you could stick your thumb in and peel it back because the armillaria digests the wood and digests the bark and makes it soft. Phytophthora just cares about killing things. It doesn't decay. This bark is as hard, if not harder than this bark. And the phytophthora, if you're trying to isolate it, is only along this little margin. I mean, there's a tiny bit left back in here. But if you're trying to isolate this for sampling this area back here is lousy. You'll have success maybe one time in twenty. If you try to isolate here, you'll get success more like one time in four. And if you try to isolate here, probably none. Although sometimes you will be able to isolate phytophthora slightly in advance of the mortality line.


Swain:

[00:54:29]

Obviously, the prognosis for something like this might be a little different than something like this where half the tree is gone--at this point even if we had things that we could treat with-- phytophthora is at least treatable. There are no visible fungal structures. You need lab testing. And I think it covered most of this, the discoloration often isn't as dark and stark as this. It may just look like somebody put a thin wash of watercolor paints over it. I've got other, hopefully I included that.


Swain:

[00:55:06]

So, there's a number of different ways, you can almost see where it's worked its way, on this wall, it's being very slow. It's probably only made an inch of progress this year. Okay, so do you remember those... Oh, a question? Yeah.


Participant:

[00:55:33]

(Inaudible).


Swain:

[00:55:33]

Yes, you will. So, it gets a little challenging, though, because the cool season phytophthoras will infect and kill in the cold winter months. But because your plants aren't don't have much water demand, they can get by on very little water in the cold winter months. So, you usually don't see symptoms, even if it's a cool season phytophthora, until the beginning of summer when those days where the day lengths really start to stretch out in June and early July. And usually that's at the very beginning of the irrigation season. So, all I can say is you'll see the symptoms in summer for all of these. It's just that the cool season phytophthoras will show up a couple of weeks earlier than the warm season phytophthoras, which we usually don't get going until June and July when people start irrigating and you'll see them show up in late July, August, September, and then it falls off again. Does that make sense?


Participant:

[00:57:12]

(Inaudible)


Swain:

[00:57:12]

Yeah, we could talk about that one for a long time and not come to any conclusions, I imagine. You know, I imagine if it's there, phytophthora cinnamomi is famous on avocado. It's a big killer. If you guys have heard of the Ashburner system of being able to use mulch to suppress phytopthoras in soil. I mean, that worked really well in Australia. He was an avocado grower who did that research on his own because he got frustrated because nobody had any answers for him on how to stop cinnamomi ripping through avocado orchards. His last name was Ashburner so that's why it's called the Ashburner system. So, it works.


Swain:

[00:57:49]

You can get control. It is about our irrigation system management. It's also about building up a healthy, vibrant soil. There are biological treatments that are fairly effective for some kinds. So, when we were talking about streptomyces lydicus, bacillus subtilis, or trichoderma, all of these things have been shown to be fairly effective against phytophthoras. Sometimes amazingly effective against phytophthoras. But again, the success rate tends to be in the 25, 30, 50 percent rate, not in the 80, 90 percent rate. The good thing is, a lot of these things are fairly inexpensive to apply and they can be applied just using a watering can, you know, simply around the base of the trees. So, if you can get them established, it's not hard to do.


Participant:

[00:58:46]

(Inaudible)


Swain:

[00:58:46]

They are technically pesticides. And some of them, particularly streptomyces of my and things like that, do have labels where they can be applied with high pressure equipment. And then you do have to be very careful because just because they're natural doesn't mean they're particularly safe. So, people have streptomyces lydicus, I believe is one of the examples. I think it may be true for bacillus as well, where if you inhale, finely volatilized aerial droplets, it can colonize your lungs. And that's not a good thing. Or, you at least, some people, more commonly people develop because it tries to colonize your lungs and your body, build a defensive response. You become sensitized to it. And you can develop some pretty serious allergic reactions to it on subsequent applications. So, you want to wear a mask. You want to follow your labels. And, I mean, I know you guys get harped on all this time about this stuff, but don't get too casual, which is why I like the watering can. Big droplets, no volatilized. You're unlikely to inhale any of this stuff. You know what I'm saying?


Swain:

[01:00:03]

Okay, so when we went back a couple of slides, remember those box shrubs I showed you at the beginning? This is what we found. And this is the color of the healthy bark tissue. It's green. We had started slicing up fairly high on the trunk. And I mean these trees. So, when I say high on the trunk, we're talking about boxwood plants that are only this high. So, when I say high in the trunk, I'm talking I started it three inches above grade, you know, and worked my way down. And you can see here's the phytophthora right through there. And this was cinnomomi as well. And it just loves fresh plantings in summer, which is why it's really better to do your plantings in the fall.


Swain:

[01:00:44]

But this, we got reasonable control with streptomycin lydicus. At least kept it from spreading because they had a huge number of box plants being put in. And it was probably on the nursery stock, we believe, and it stopped spreading as soon as we put that stuff in. We could not save, obviously, these plants. They were gone.


Participant:

[01:01:07]

Does anything else look very similar to that? I know you said it could only be diagnosed in a lab so obviously we'd have to send in a sample, but there anything that just like visual inspection might be a look-a-like to this?


Swain:

[01:01:21]

There are plenty of things that can but generally speaking, if I come up with this and I do a fairly thorough-- so we we're asking about Japanese maple earlier--armillaria on Japanese maple causes mortality way far in advance of the actual hyphae. It's really surprising. So, you can get sometimes like six inches or a foot of mortality without any hint of the fungal mycelia coming up through it. And mycelia are how I field diagnose armillaria. So, I have to be careful with some plants, especially ones I'm not used to working with. And if you're going to say it's phytophthora not armillaria, you should probably go pretty far. My suggestion is you go dig into the soil and start digging out the roots and checking those roots as well. So, you know, Japanese Maple and Sausalito. I had to take a picture of this because I've just never seen it this bad before. There is nothing that's going to bring back a pretty heavily invested plant. None of these therapeutic treatments for phytophthora include Subdue Max. But the problem with Subdue Max is it's really, it's labeled as a fungicide, but it's really a fungi stat. It stops things in its tracks when you apply it, but it doesn't actually kill the fungus. Or the phytophthoras aren't true fungi. But you know what I'm saying. So that means that if you're not killing it, then it just takes time for it to overcome the Subdue. And that's what happens. So, we got people who are swearing by Subdue Max. And the problem is, if you repeatedly apply this stuff, you will develop a super phytophthora in short order. Because it does not kill it, it just stops it. So, if you've got valuable landscape plants, it can be a tool. But I don't recommend it. Phosphonate compounds will work better in terms of them stopping things. But again, they're not very successful therapeutically. They tend to be better for stopping the next Japanese maple down the line from getting it after this one died. Yeah?


Participant:

[01:03:48]

(Inaudible)


Swain:

[01:03:48]

I'd cut this down. I'd stop watering it immediately and let it sit all summer. I'd dig the roots out not because I necessarily--just because phytophthora won't care. But my concern is you could have our armillaria sitting on your soil someplace. And if you've got a dying root system, then you could have phytophthora and armillaria. And that would be really bad. So, I would dig this root system out as a matter of course. Then I would treat with one of these bio rational fungicides that we've been talking about. Hopefully, I could get it established. And ultimately, it's just essentially a prayer. Yes?


Participant:

[01:04:33]

(Inaudible)


Swain:

[01:05:00]

Yes. I want to hold that just to make sure I don't run out of time here. So, what I would do for phytophthora is these suppressive micro-organisms. So, here's bacillus subtllius, trade names are Rhapsody and Serenade. And streptomyces lydicus, Actinivate, ActinaIron. And those are the kinds of things I would be considering treating the soils with to minimize risks to future plantings.


Swain:

[01:05:27]

Other pathogens. So, we've covered these. I've left verticillium out. It is technically a soil dwelling pathogen, but it's more of a clogger than a root thing. And often you can find it pretty high in the plant. It's a vascular wilt. The one other thing that I have run across in the North Bay that fits into this group of things that you might find is amata flora. Although I've only found it twice in the 12 years I've been here. Now, this leaf, it causes the same type of symptoms that we've been seeing. It does get into the bark. If you peel the bark away, you'll find this intermingled in the bark. But you'll also find little clumps of it in the soil. It's very pure white. And I've mostly seen it on things in rosacea. I know it attacks other things. Often you don't even need to go in you. It is on the outside of the bark. But there are lots of things that can grow on the outside of bark. So that makes diagnosis of this fairly problematical. But when you go into the bark, you'll find dead sections of bark with white little patches. And so, it starts looking like armillaria. But armillaria is never on the outside in a white, fluffy fungal form. It's either on these rhizomorphs that look like shoestrings, or it's in mushrooms or those kinds of things. So, it's not common. But I thought I'd mention it just because it has been found.


Swain:

[01:07:01]

So back here, what was this? This was a phytophthora, but it looks like it could have been, you know, if especially if this was the southwest side and that got a little more sun than this one, it could have been sunburn. It could have been all kinds of different things. This is just chronic drought. How do we know that? Well, there were a few clues when we started looking at it. It's an Eichler. How many places get built wit--when did they build Eichler’s? Anybody know? 50S and 60s. Exactly. That tree was planted in the 50s and early 60s in a lawn. And this was planted in Marín when they didn't have water restrictions because there were only a few thousand people in Marin anyway. Right. So, people watered the snot out of these things. And this fruitless mulberry has been living on its reserves and eking by for 50 years. But look at the landscaping now. Is that lawn? How much water is this poor thing getting? I've got called out by this whole HOA area because they thought they had a disease and the disease is called high water prices. These trees were healthy-ish. I mean, but they just are not getting the water that they've needed for decades.


Swain:

[01:08:20]

And then this is root weevils. Finally, this was none of the above. We can talk about doing a solid root crown inspection and all this other stuff. And I did root crowns inspections on these and the root crowns looked pretty bad. It was just not clear. And in this case, it looks like a root crown problem because the distributions are fairly uniform in that they are attacking mostly the young new leaves and the things. This poor soul had an ex-boyfriend that knew she loved to garden, and he came in with a sub-lethal dose of Roundup and hit her entire garden. And I kept doing root crown inspection, after root crown inspection, trying to figure out what the heck was going on here. And that one took me a long time to figure out. So, there is a company that you can send your samples to in Woodland that will run glyphosate, you know, for poisoning symptoms. I'm sorry.


Participant:

[01:09:26]

The ex-boyfriend test.


Swain:

[01:09:26]

Yeah, the ex-boyfriend test. Yeah, and it's very informative. So, when you really get stuck and it looks like it could potentially be herbicide, you can always send it off to them and go.


Swain:

[01:09:42]

So, root crown inspections. Here's a case so you can see. I did my cut in here and it was dead there. But in other cuts, it had been this green color, and this is exactly how you get it done to figure out. Now, all that said. You start, you work down, you keep going down several inches below grade because you want to make sure that it is actually something that's killing the roots and assess conditions of the roots, assess the conditions of the soil. It's all part of figuring out a bigger picture. This one I got wrong. I mean, that's the end result. I'll go back to that in a second.


Swain:

[01:10:27]

The way this ended up showing up was somebody brought me a Japanese maple. And we all know the Japanese maples get verticillium at the drop of a hat and they tend to get verticillium in these drought and drenched irrigation cycles. So I took this Japanese maple and I cut into it and I got the classic vascular streaking that you get on bigger branches when you just slice down and you say, "Oh, look, black streaking, Japanese maple. No problem. verticillium, done." And so, I started telling them, here's what you need to do. You need to make sure they get more consistent moisture. Yada, yada, yada. And they kept looking at me like I was on glue, you know. And I'm like, what? And they're like, “No, we wash our car next to that thing all the time." You know, "that Japanese maple staying moist a lot. In fact, if anything, it's getting over watered." And that's what made me stop with this whole thing because, yes, it had verticillium, but it also had phytophthora. And that's when I started doing the crown inspection and going down and figuring out what the real problem was. Because I diagnosed it and it didn't fit, you know, your clients are your best tool, if they tell the truth, which they don't always.


Swain:

[01:11:41]

So water management, all of this comes down essentially to water management. I mean, root crown inspection. So, assess the water status. Typically, 12 inches below grade. So, what we're looking at here, you know, we've got a landscape, the top three inches have maybe even four inches are moist. And below that, it's just bone dry. This is really common in California soils, and it's what we're trying to get, what everybody's been talking about here, doing deeper irrigations. And that works great because it allows your plants to go longer between watering. And it allows this top area to dry out. And that's where the pathogens tend to be, is in those top six inches of soil because that's where the air is. So, we want this to be flipped, ideally when we do this. We want to be able to probe down a foot into the soil and have a little bit of moisture down eight to 10 inches. And we want the top to be dry. In a perfect world. Now, you know, so this was telling us something. This is one of the reasons I like soil probes instead of just like some little meter, you stick into the soil, you know, because you actually get to see the texture, the organic matter content, all that other stuff. So, let the plant tell you how it's doing. Check the whole soil out. And remember that the effects occur over years. So, your site history is going to be important. And remember to be humble because otherwise you're going to screw it up. And that's it.


Participant:

[01:13:13]

(Audience Applause)


Swain:

[01:13:13]

Okay, so we had at least one question on asamite and treatment of sudden oak death infected oaks and how much asamite can play into it. So, I'm going to just talk. Some of the research on this is my research that I did with Mateo. Some of it's just Matteo's research that I'm going to be talking about. So asamite as a product was not necessarily tested. What was tested was calcium additions in the form of gypsum and with and without Agri-Fos. So Agri-Fos, if you add gypsum and you apply Agri-Fos, gypsum seems to have some kind of synergy that is not understood what's happening. But you can measure, according to Matteo's research, improved resistance with the addition of calcium, whether it's in gypsum or oyster shell or asamite. There are number of different forms of it. But if you can get calcium into these trees with Agri-Fos, it seems to help. Whether these calcium helps without Agri-Fos, I don't know. My suspicion is that it doesn't necessarily help, for a number of reasons. The bark scribing thing is a whole different story. And this is a story about why science matters. And it's a little bit about folks doing single off experiments and then coming to conclusions or even a low replication number of experiments. And this is a whole other talk I have and I’m going to condense it into three minutes. So, if I missed some details forgive me.


Swain:

[01:15:10]

But essentially, Oaks, as a general population have this huge range of genetic diversity and a lot of the Oaks out there are quite resistant to sudden oak death. We don't think of it that way because those we see a lot of trees dying and we see half of a forest dying it's kind of alarming. On the other hand, the guy who had my job before me, tried bark scribing. He had a whole bunch of different-- and there's good reason for it. So even I saw it. When I was doing sudden oak death work, almost 20 years ago now. And I would go in and I would scribe, we'd have these bleeding spots and people would say, "Is my oak infected?" At the time, we didn't even know Bay Laurel was the infective agent. So, we would just go sample the oaks directly. So, I'd cut in and I'd find the edge of the canker and I'd sample from the edge of the canker. And I'd plate it out and it would grow out or not, you know, that sort of thing. And then I'd follow up a year later to see how that tree was doing. And half the time, I would see that the tree had produced nice callous tissue around the infection, and the infection had cracked and shrunk and dried out because phytophthora likes things cool, dark, and moist. And I had just made it warm, dry, and light, right. So, it made sense. When I looked at it, I was like, wow, this bark. Treatment. I'm treating them just by sampling for them because I can see the phytophthora infections shrinking and drying.


[01:16:43]

I wasn't alone. I was doing this work, but so was Ted Zwicky and a bunch of other people, and they saw the same thing. And so was my predecessor, the guy who came before me. So, this hypothesis was, what if we just slice into the trees and we use that as a treatment? And there's reason to think it worked, because if you look and you see IPM and you look on the citrus sites, and even today there is at least one site that still has not been updated. They say bark scribing is an acceptable treatment for infected citrus trees. You just cut the bark. You don't go all the way to the wood. You just go cut the bark down to about halfway through and you will cure the infection. So, it was in the literature on citrus for phytophthora. And so, it made sense. So, my predecessor went through and did about 200 trees in an uncontrolled study. The problem is it's an uncontrolled study. And why do controls matter? Well, it’s simply this. How do you know that you're actually being effective? In other words, how do I know that, say, if I have a canker that's this big, how do I know it's that same size canker I'm comparing to this canker? How do I have something to compare my treatments to that isn't shaved? Right. I'm shaving one tree, so I'm treating it. How do I have another comparable treatment that I leave alone and watch that canker grow? Right. I need to have a control. That's a scientific control. If I cut into it, I'm treating it. So, we tried to find noninvasive ways to detect cankers and things like that. Unable to do it. Long story short, doesn't work. So the only way to do that is-- and this is why my predecessor never controlled any of his experiments--because you can't cut into it as soon as you cut into it to figure out what size the canker is at time zero, you've just treated it.


Swain:

[01:18:40]

Okay. He went out, did about 200 trees, and his philosophy was, I'm just going to do about 200 trees and if it really works, we'll see it over time. And he came to the conclusion that this probably works. And other people heard about the research and started treating with bark scribing. I had to do with things a different way. I got asked to clean this mess up. So, I went out and I infected trees with a known size of phytophthora at time zero, plugged it into a whole bunch of trees. This took a long time to put together because when you ask people--small trees are all fairly resistant to phytophthora, the big trees are the ones that are not. So, I need to take a bunch of your big, mature, gorgeous live oaks. Can I infect them with a deadly pathogen and then measure the effect on your trees? And I need to do it not just once. I need to do it like 30 times. Anybody willing to donate 30 Heritage Oaks to me? The answer is no. People value those trees. So, it took me three years to find sites on state park land and other places like that where people would let me infect trees that were of a certain size and risk killing them. And what we found out at the end of all of this is that the trees killed the phytophthora a huge percentage of the time. Probably 50 percent or more. So that means that when people are running these things and they're saying, I had an infected tree and I did X, Y and Z to them. And you can't figure that out if you don't control. Right. But they if they say I did X, Y and Z to them, if you don't know what the background kill rate is, you have no idea how effective your treatments are. So, I had people coming and telling me that wind chimes worked for curing phytophthora remorum. I had people coming and telling me bark scribing worked. I had people telling me that every concoction under the sun you could spray on trees was what was effective. And the truth is, most of them were not. Most of them were simply people taking their treatments and giving credit to themselves for being a genius and figuring this stuff out. When the tree was doing all the work. The tree was killing the phytophthora when it got to this size. And then they were cutting into it saying, "Oh, we caught it in time. It's small." You know. and then they cut into another tree and it's like, "Oh, it’s way too big. It's way too late." The big tree could not stop the disease. And so, nothing you are going to do is ever going to solve it. The other tree with a small canker already stopped the disease. It did not matter what you put on it.


[01:21:14]

So, bark scribing is a treatment, really, although it looks very--I was very convinced when I started, this is like a no brainer. I should be able to get this slam dunk and it turns out we were wrong. And that's why science matters and that's why it's replicated. And that's why you have to have controls, because otherwise you're just you're going to get fooled by your own ideas because everybody loves their own ideas. They're your children. You know, I mean, so the moral of the story is doesn’t believe everything you think. And there are a lot of people who do. Yeah. Question?


Participant:

[01:21:49]

(Inaudible)


Swain:

[01:22:14]

So, we're talking about my bark scribing study? It's a great question. And that's actually in that talk. You know, I just tried to abbreviate it. Yeah. One of the problems with our study was the trees killed the pathogen about half the time. And I was trying to see efficacy of bark scribing, so that meant I went in with 60 trees. I got 20 at three different sites. Right. And that was a lot of work, just getting those 60 trees. Let me tell you. Right. And in most of the sites, half my samples dropped out. And then on another chunk of the things, I lost quite a few trees to beetles coming in and saying, "Oh, look, it's a phytophthora infected, and they nailed that thing and it was gone. I ended up with a very small number of trees that I had to try and use somewhere in the neighborhood of 22 trees left out of 60 that I had to sit down and try and run my statistics on. And it's not a really great sample size for running statistics. So, my error bars are huge. So that is my disclaimer. When I say it doesn't work. There are some differences, but they're not statistically significant because if in order to get statistical significance, I would have to have a much larger sample size. But there's a lesson in that, too, which is any treatment that has a small enough effect that you need a huge sample size to find it isn't going to be significant on a landscape scale. Because now what it's telling you is your efficacy is somewhere around five to 10 percent. So, bark scribing might be worthwhile, but it might actually be effective. Is it cost effective? I don't know.


Swain:

[01:24:01]

I can pretty much tell you if it's effective, it is only effective at a fairly--I'm just not spitting the words out as well as I would like today. They talk about statistical significance and landscape significance are two different things. To sell people a treatment on bark scribing for X number of hundreds of dollars when it has a chance to make a five percent difference on the survival of your tree may not really be worth it. That's what I'm trying to say.


Chris:

[01:24:33]

How much bark is taken off when you do the scribing?


Swain:

[01:24:34]

That depends on the size of the canker. Remember, that walnut tree.


Chris:

[01:24:39]

So it's just the canker?


Swain:

[01:24:41]

Yeah. Otherwise, it's sort of like, yeah, we had to destroy the village in order to save it. Right. If you strip all the bark off of a tree, you're probably creating more problems for it than you're solving. Okay, well. No more questions? Good. Thank you very much. (Audience Applause)