Plant Problems & The WSU Pullman Plant Pest Diagnostic Clinic with Rachel Bomberger

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Contact Rachel Bomberger via email at
or by phone at 509-335-3292 or 509-335-0619.

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Episode Transcription:

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Drew Lyon: Hello and welcome to the WSU Wheat Beat Podcast, I’m your host Drew Lyon and I want to thank you for joining me as we explore the world the small grains production and research at Washington State University. We have weekly discussions with researchers from WSU and the USDA-ARS to provide you with insights into the latest research on wheat and barley production.

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Drew Lyon: My guest today is Rachel Bomberger. Rachel is from Reno, Nevada. she did her undergraduate work at UC Santa Cruz, and as a banana slug she worked on clover speciation. She got her master’s from Oregon State University and immediately went to work as a Plant Pathology Diagnostician for the Nevada Department of Agriculture. In 2015, Rachel became the head of the WSU Pullman Pest Diagnostic Clinic. At the clinic, Rachel works on plant problem diagnosis on all plant species, though the majority of her samples come from wheat, potato, pulse, and tree root systems. Hello Rachel.

Rachel Bomberger: Hi Drew.

Drew Lyon: So, what does a typical day in the clinic consist of for you?

Rachel Bomberger: So a typical day in the clinic, especially during the busiest time of the year, involves plant samples coming in from somewhere and then me spending a couple of hours working through the samples. So usually this means I’m at the microscope getting my hands very dirty, messing around with root systems, running different tests. There’s a lot of different technologies that researchers put out that then get utilized in diagnostic clinic, so running around from different samples. I can be wrist deep and some rotting potatoes and then jump to wheat and then all of a sudden, they’ll have a fire blight sample come in. So, it’s very different depending on what time of year it is.

Drew Lyon: That doesn’t ever get boring for you then?

Rachel Bomberger: No, that’s the best part.

Drew Lyon: So, there’s a lot of different things that can go wrong with a plant, a lot of things that can look very similar to one another. How do you go about figuring out what a particular plant problem is that comes into the clinic?

Rachel Bomberger: So normally when I get a plant sample and the first thing I do is I ask people to actually submit a sample submission form where they fill out a bunch of information. But before I even look at that I immediately dig into the plant and what I do is I try to look for any of the symptoms that I can see. You know, is it yellowing? Are there characteristic symptoms like Tim Murray talks about cephalosporium stripe produces really unique symptoms? So, I try and pay attention to, what do I see? If I know nothing about this plant what do I immediately pick up on? And then from there I start microscopic examination, so I actually look at the plant from head to toe, see if I can find any physical evidence of the pathogen. Say, stripe rust leaves kind of this dusty orange material left behind. So, I’ll go through and see if that’s there as well as I’ll check the root system. Maybe there’s some damage to these roots, kind of follow that path, so that’s where the word pathology comes from. It’s figuring out what’s gone wrong, so I start that path and if I find yellowing, well I want to look at the root system see what’s going on. And from there, if I find symptoms that indicate there might be a biotic, so a pathogen-based problem caused by fungi or bacteria or even viruses or nematodes, I’ll go from there and then I’ll start doing various tests to see if I can get the organism to grow out. If I need to detect pieces of its DNA in order to figure out what’s going on and then sometimes what happens, actually 50% of the samples that come into the clinic are actually not caused by pathogens, they tend to be caused by nutrient disorders, such as soil issues. So, if there’s pH problems, compaction, water logging or drought, you know those can produce actually pretty similar symptoms to biotic. So, once I’ve ruled out that pathogen-based cause then I start to go into the environmental side and then eventually I do look at the sample submission form to help me fill in those clues, but I do actually wait ’til a little bit later, the way I don’t accidentally bias myself onto what the grower, the client thinks might be the problem.

Drew Lyon: I know in my experience, you know people tend to, when you go into field to look at the problem you tend to look at the above-ground symptomology, but I’ve always been surprised how many those above-ground symptoms are actually caused by what’s going on underground and yet, do people send you good samples with roots? Because a lot of times, what you’re seeing up top is actually the result of roots and I know that a lot of people perhaps don’t think about that when they’re collecting a sample to send to you.

Rachel Bomberger: Absolutely, it’s far more shocking to see a yellow plant and want to know immediately why the plant is yellow and so, when you take that sample you collect just the yellow leaves. When a reality the source of that problem is often in the ground. This is why I always encourage people please send whole plant samples because it lets me see, okay, so we’re seeing a symptom of yellowing but is the root cause at the roots? That was a good pun there. [Laughs]

Drew Lyon: It was.

Rachel Bomberger: But so, that’s what we’re trying to do is to tease out, you know what are the symptoms that we’re seeing and what are the causes? And that’s really that’s why the types of samples I get are a little bit more ambiguous. But people are pretty good about sending the whole plant most of the time especially in a wheat system where these plants are actually small enough to, it’s probably easier to just rip out a couple of whole plants than to meticulously go collect individual leaves anyways.

Drew Lyon: So this is the Wheat Beat Podcast, what’s the most common wheat problem you see coming into the clinic?

Rachel Bomberger: It kind of goes back to what we were just talking about. I get a lot of symptoms of, I have yellow or poor growth, some stunting, just unhappy looking plants and again, it goes down to the fact that it’s actually starting at the roots. Because that’s a much more ambiguous symptom then stripe rust where you can see that organism. So, a lot of what I get on wheat are things like Pythium, Rhizoctonia and then later in the season I do get some Fusarium. But those early root rotters that are taking advantage of young seedlings, that’s what I get fairly frequently with wheat.

Drew Lyon: What are some of the strangest things you’ve seen come through the clinic?

Rachel Bomberger: The strangest thing I’ve ever seen is when a homeowner is very concerned why nine different types of plants were dying. That was because she accidently spray-painted all of them and was confused that spray paint might kill a plant. But the stranger’s wheat sample I’ve ever gotten was, unfortunately, it was you know, a Friday at about 4:30 p.m. and I get a sample through the mail that has very odd bends at a lot of the nodes of the wheat plant. So, it’s bending at multiple 45-degree angles. So, the plant looks very odd, unfortunately the folks I rely on for these oddities, no one was available. So, it was just me trying to figure out what was going on. So, when I’m stuck I tend to do a Google image search or some other form of internet search and so I typed in, “odd looking, odd bending wheat,” and I found a picture that looked pretty close to what I had. Clicked on it and started reading this article. And it starts talking about gravitropism which made a lot of sense of the fact that gravity is telling the plant to grow one way versus another, and then I read a little bit further and starts talking about crystals and magnetism and I realize I’m probably getting more and more off of what it should be. And then at the bottom I see so I knew I was off. So that one was odd because I made the rookie mistake of looking through the internet for an answer. But that ended up being the plants had gotten knocked down earlier in their lives, and we’re constantly trying to correct themselves, so it was gravitropism. As the plant fell down it kept trying to grow upwards again so it just got some odd articulation at the nodes.

Drew Lyon: Interesting, so collection of a good sample is very critical to your ability to diagnose a problem. How should people collect samples and prepare them for delivery to you in the clinic?

Rachel Bomberger: Absolutely Drew, good-in equals good-out to the better sample I receive the better diagnosis I can provide. The best samples are whole plants and multiple whole plants. Having multiple whole plants means I’m not working with one damaged root, there’s a bigger opportunity for me to find more evidence and it increases my likelihood of actually getting the pathogen to grow out from the plant in the laboratory. And again, it lets me kind of check that patient, if you will, from head to toe that way we can catch and match the symptoms to what actually might be the cause. The other thing that is very nice is to have a healthy plant to compare and contrast to because there’s a lot of times where the healthy plant might actually have the same disease present, but it could be less. So, we can have a really sick plant and then healthy plant might still have that pathogen but there’s something else going on with this sicker looking plant, that then allows me to tease apart. You know, just because I found Rhizoctonia or Pythium doesn’t mean that that’s the full picture. So, when I have a healthy plant that allows me to figure out what other issues might be playing in, you know, is there a low spot? Is there a pH issue? Is there a chemical issue? So, the more plants I have access to the more I’m able to tease out better information out.

Drew Lyon: And I imagine if they can report on any kind of pattern in the field, I deal with drift issues sometimes and you know, drift has a definite pattern in the field and if you didn’t record that it might be difficult to know that, that might be one of the problems. So, you ask people to send you a description of patterns or where this is occurring?

Rachel Bomberger: Yes, there is a sample submission form that I asked growers or industry professionals to fill out and that asks a lot of these questions, you know, what variety is the plant? When was it planted? Where is it planted? And there’s even sections for you to fill out this is what the pattern of the field looks like, this these are the symptoms I’m noticing, because believe it or not, the symptoms a grower or the industry notices aren’t always the symptoms I’m going to notice because I have a different eye and a different background. I can’t grow plants to save my life, so I have to double-check that I’m following the same track that the growers are. So that just kind of allows me to make sure that I’m not skipping the thing they’re concerned about. Because I’ll always go for the roots if you give me an option. And then again, you know, what patterns? How is it watered? A lot of these, they seem like minutia, they’re little tiny details but again in a system where we find that the healthy plant and the sick plant have the same pathogens on them, that’s actually where we find the most important information. You know, what are the other conditions the plant is growing in? Do you know your pH? What was growing before that? What type of soil do you have? And then oddly enough, knowing where the plants are growing in relation to, you know, the address you might fill out on the form at first it is where the plant is. I can provide a lot of information because there’s totally different weather patterns that these plants might encounter.

Drew Lyon: So if people want to learn more about the Diagnostic Clinic, is there some place they can go to learn more about it?

Rachel Bomberger: Yes, the website is Again that’s, plant, p, l, a, n, t, Path, p,a, t, h dot wsu dot edu slash, diagnostics.

Drew Lyon: All right, thank you very much, Rachel.

Rachel Bomberger: Thanks, Drew.

Drew Lyon: Thanks for listening to the WSU Wheat Beat podcast. If you have questions for us, that you’d like to hear addressed on future episodes, please email me at You can find us online at You can also find us on social media on Facebook and Twitter @WSUSmallGrains. Subscribe to this show through iTunes or your favorite podcasting app. The WSU Wheat Beat podcast is a production of CAHNRS Communications in the College of Agricultural Human and Natural Resource Sciences at Washington State University. I’m Drew Lyon; we’ll see you next week.

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