Plant Disease with Lori Imboden

April 2, 2021

Frequently Asked Question

How do I properly sanitize my tools to prevent recurring disease?

On our episode, Lori mentioned the importance of sanitizing tools and seed starting pots to ensure diseases don’t carry over from one season to the next. Here is a great article highlighting methods for ensuring your equipment is sanitized:



Video Transcript

[Abby] So I'm going to invite Lori and Isabel to turn on their cameras. As a reminder, if you have issues at any point during the webinar, there's a Zoom helpline for MSU Extension that you can reach out to. So welcome to Cabin Fever Conversations. Today is our eighth episode in our 10 part series. We're getting towards the end and it feels fitting that we're starting to see warmer weather, more sunlight. And that folks will want to be in their gardens rather than talking about them soon. So I'll turn it over to Isabel to introduce today's featured guest, we are excited to have her. [Isabel} Yeah, So today we have Lori Imboden, who is a consumer horticulture educator in Oakland County and a plant pathologist by training. And usually she's behind the scenes. And today we have her in front of the camera. Pretty thrilled about that. Today we're gonna be talking about plant diseases with Lori So happy to have you here in front of the camera, Lori, and really happy to have you here every day that you're helping us. It's exciting that everybody gets to see you today. [Lori] It's fun to be on this side of it. I'm excited. Nice tulips! They a breath of spring. I've enjoyed them. Yeah. There's a little bit or early spring and it keeps them away from the deer. [Isabel] Smart. So we wanted to start off by asking you, What about plant diseases brings you joy? [Lori] That's a funny question but what about saying, well, I don't enjoy it. You know, I don't enjoy seeing people lose plants that they care about or something that makes them sad. I have had plants that I care about that I've lost to disease, but I do find it interesting. And I find that figuring out the disease process or helping to identify a disease or helping someone solve a problem. To be sort of like a puzzle and problem-solving. And I do, I do find that gratifying, so I don't want to say that anyone's disease brings me joy, but I do like being able to help people with what I know. That is, that is very rewarding. And I like to solve puzzles and solve problems. And there's a lot of that. [Abby] yeah, I love that. It's just kind of using your observational cues to figure out what deep, larger picture is going on. As a fellow puzzler, I can see, I can see why that would be joyful, although it's hard to keep that in mind when you're like scrambling to save your tomatoes or something like that. Yeah. So Lori, I know you've done a lot of degrees related to plant pathology and things. So there must have been something early on that got you really geeky about it. And I'm curious if you could share more about kind of what that motivation is or where that geekiness comes from. Puzzle solving is a lot of it. So there's a lot of ways to study diseases and to study plant pathology. People can be looking at big ecosystem problems or issues with a particular crop. All of the work that I did that I worked mostly in university labs and a little bit for the USDA. But all the different places where I worked and the systems that were done, what we were looking at was rather than that big, that big population size problem we were looking at. We have a scenario where there's a host plant I worked with at different points, bacteria and fungi, although there's other things that can cause diseases. You know, you have that host plant, you have that pathogen, and you have an environment that's conducive to disease developing. You know, what's actually happening? Because plants have immune systems. They're not exactly like ours, but they have immune systems, So why is a planet able to defend itself against one pathogen and not another? And then pathogens have to find ways to get around those immune systems. So how is a pathogen able to infect one plant and not another? And then there's something we'd kind of refer to as biological warfare. So the plant defends itself and then the pathogen comes up with something, and the plant has another strategy and then over time these really complex relationships evolve and, and that's really key to understanding and managing diseases as well, is understanding that some of these relationships are very specific. You have a pathogen in your yard, but it may not necessarily infect everything else because it's, it's really only got the tools to infect few plants that are in the yard. That was what got me all excited about it. [Abby] Yeah, it's, it's fun to see that reciprocal development of like things adapting and developing to co-exist or survive the other. And how in some cases, I mean, I've seen, I've seen spaces where disease is present and plants find ways to still thrive with it. And kind of like reciprocal, everybody trying to survive. And not necessarily, you know, the pathogens aren't thinking about it as like I'm taking over this plant. It's just "what are the tools that I need use to survive" and the kind of evolution that comes from that. [Lori} It's like watching a nature documentary... are you routing for the gazelle or are you rooting for the lion, right? Yeah, I mean through. [Isabel] So do you have any examples of really weird plant diseases or really weird examples of this biological warfare between plants and diseases. [Lori} Well, I mean biology, if you like weird examples, I mean there's tons of them in biology. Some of the pathogens that I find really fascinating are ones that form galls. So actually have a whole talk on this though. There might be somebody out there today you've gotten to here me talk about galls for an hour. But galls are kind of an interesting part of that, that interaction because a gall is something that is actually formed by the plant, but that benefits the pathogen. I guess it might be a microbe like a fungus or a virus or bacteria, but also insects and some other plants can actually do it. So they actually trick the host plant into making something for them. So the plant puts its energy and its molecular machinery into making a food or a house for it. One example I've got here I'll share real quick is Agrobacterium tumefaciens. Oops. I lost my screen-sharing. Well, it looks like when we crash we lost something but I'll just describe it. So when we have little crash before we went live, so not everything recovered. So agrobacterium is a bacterium and i it's one of those pathogens that's able to infect a lot of different types of plants. And when it gets inside the plant it actually shoot some of its genes into the host plant, and gets the plant to, first of all, make this weird, lumpy, bumpy gall, and they can be quite large. There's huge ones that'll happen on trees and very small ones that'll happen on vegetable type plants. And inside of it, inside of that will gall it's making these amino acid derivatives that the bacteria will eat. So it's like, hey, I'm going to invade you and you're going to make me a house and you're gonna make dinner, then the plant just does it because the pathogen has that ability. And there's, you know, there's insects that do it and plants and there's a lot of different things that make all these galls and a lot of the agrobacterium ones are just kind of lumpy and a little gross looking, they look a little bit like brains, but some of them are really beautiful and different colors and shapes. And so I find gall inducing organisms to be really interesting. [Abby] In general, are the plants then able to survive and continue to do their own plant thing even with the gall and then kind of continue to provide host to this external specimen, or does it kind of like create the house, make the meal, and then doesn't have enough resources to survive itself. [Lori] It depends...A gall is a mechanism, but there's a lot of different organisms that cause them. So some of those organisms on a lot of the goals that form on deciduous leaves. So those leaves, there's a lot of little insects or a gall wasps, especially that'll form on leaves and those fall off in the fall. It doesn't hurt the plant to have these gall insects on there. In fact, they're really cool and interesting. Some of them are more problematic like that when I was talking about crown gall. That's something that if it's found, you'd want to get that out of, out of the space. You're going to get that out of the garden because it can spread and it can be problematic. So it depends. They can be really bad or they can just be kind of a pretty fun addition to your plant and our nursery for new life. [Abby} So I know a lot of folks approach diseases as "Oh crumbs! I have a disease in my garden and I, now it's ruining my plant and I need to figure something out about it." But there's the flip side of that, which is creating environments that prevent plants against being susceptible to disease, right? So I'm wondering if you could share some practices or tools or kind of like parameters to keep in mind, both when thinking about garden planning, which I think a lot of our audience right now is engaged in, is figuring out where they're going to cram as many plants as they want to in.... As far as kind of general seasonal practices to help limit the spread of pathogens? [Lori] Yes, and with pathogens, There are all different kinds and they have different niche environments that they like. But there are some general practices that if you follow that, as a general rule of thumb can help you prevent those problems in the first place. The first thing is cleaning, so sanitation. That includes cleaning things like tools. So I am just starting to do some seed starting. And so before, and I'm reusing some of the cells that I use last year. So I made a 10 percent bleach solution. So one part household bleach and nine parts water. And I soaked my seed starting things in there to make sure that if I had a little bit of damping off last year and I want to make sure I don't carry that off. Don't put your tools and that there's some other ways to to sanitize those. And we have something that we will send you afterwards that's got some tips for specific situations. Sanitation also extends to outside. If you have a plant that pretty clearly showed signs of diseases last year, well, it's fine to leave most of the plants out and do fall and winter. I think it's interesting to see the snowfall on the plants that have already completed their season. But if something had a disease, you want to clean that up. Don't leave that around because that leaf litter, the stocks. That thing. That's something that can inoculate another plant the next year. Another thing is bringing in healthy plants. Like I know we all love to rescue plants from clearance section, but don't ever do that. But I'm just saying do a really good once over, make sure that maybe it's there just because it's not flowering anymore. People aren't as excited about it. If you start to see things like rot happening on it. it's exciting to bring something to life, but not at the risk of potentially making your other plants sick and bringing that in. You can also, if you have a disease problem that you're aware of, you can pick plants that are resistant. So if you're having, there are certain types of fungi that cause wilt diseases. So they sort of plug up the water transport system in tomatoes and they cause the plant to wilt regardless of how much water you supply. So if you have one of those wilt diseases, particularly verticillium and the fusarium wilt. And you have those problems with your tomatoes. When you're picking tomatoes seed for the next year, you can find tomato seeds that are resistant to those diseases. So then you just don't have to worry about treating it because you've got something that's just going to be able to tolerate that in the soil. And then you mentioned crowding as many plants in as possible. So I know when we're planting little tiny plants and they say, your tomato plant, it's this big, but it needs to be like, you know, a pretty long distance. And it seems unbelievable because it's only this big, but it's going to be a very short time before you have a very large plant. And when those plans are packed in their environment, where all those leaves are there's not a lot of air movement and you can have high humidity and low air circulation and not all pathogens, but there's a whole lot of pathogens who think that's a really great environment and they're going to grow. Making sure you've got that recommended space. That your pruning out things...let airflow in. Those are all good things, good practices that can help avoid a lot of different disease problems. [Abby] So choosing your plants to make sure they're disease resistant, whether it's variety or healthiness of plant, right? I think about when plants at young ages get really stressed for nutrients and things like that, that it just diminishes their defenses a little bit. And then also that the cleaning up in your garden and making sure that things are spread out in a way that doesn't promote a hot jungle condition in your tomatoes. And, and maybe just choosing one less plant, maybe more than one. But when you're in limited space, really be like, "I think I can fit one more in there." [Lori] It's really hard, especially if you're planting a new space and they're just so little and you think, "Oh, it looks so empty" Yeah. I just go with a completely different plant. Go with something that's different. You might look for resistant cultivar. You might just say, maybe it's time to put something else here. [Abby] Yes, so we've got the same disease pattern year after year and it's just consistently wiping out that plant, give it a couple of years of a break, right? Maybe have your friend grow those plants for you. I'm trying. Let me take over their land for growing beans because I've had a bean disease for three years and I can't seem to take that lesson in stride of maybe I should pause for a year and let the pathogens kind of die out a little bit. [Lori] That it's hard, it's hard. [Isabel] One quote, that always sticks with me when planting your garden is begin with the end in mind. Think about what those tiny seedlings are going to look like in August. How they may crawl over each other and be, hot jungle conditions. [Lori] Yeah, create that nice moist environment. There's a lot of pathogens that think that's really great. Yeah. [Isabel] So what do you think are the best ways to manage disease in garden? [Lori] You can do everything right. You can have a healthy plant like Abby said, you can do all that cleaning out. But pathogens have been around for a long time and they've been exploiting plant weaknesses for a long time. We can't prevent them all. So when they do have them, first thing is is to stop and to step back and to look at the whole situation. I'm a fixer, there's a problem and I want to make it better. And so our first instinct is to do, to do things and that's not always helpful. So the first thing, is a practice we call integrated pest management, just to really step back and look at the whole situation. And so when you step back and you look, and you can look at the whole situation and the first thing that you want to do is make sure you know what plant you're working with and do your best to try to identify the disease. Because if you don't know what you're dealing with, any steps that you take after that may not necessarily be helpful and they might be harmful. So sometimes we don't think about some of the things we do. and actually further stress out a stressed out plant. So there's a lot of pathogens that are hanging out on the plants might cause a disease but aren't going to threaten the life of the plant. Every fall we get a lot of pictures of maple leaves with black spot on them. And that is the disease that gets infected on maple trees. The plant gets infected in the spring, that fungus grows. in a tree during the summer and then by fall you have these black spots called Maple tar spot. And they're not necessarily beautiful, but they are not a threat or a problem for an otherwise healthy tree. So going to the trouble and expense of treating a massive maple tree early in the season to prevent some cosmetic spots on leaves that are going to fall off. That's something you can live with and your tree can live with, and it's okay. So, then also we talked about times that you might just get rid of a plant. And I have a but right here was a very poorly sited lilac tree in my yard and it was in a shady spot and it's clearly cultivar that gets powdery mildew and it's just covered in powdery mildew most of the season. And frankly, I just decided it needed to go. I don't want to fight the powdery mildew, didn't want to look at it. And I just decided to find something better suited for that location. And then if you are going to do some sort of treatment. So you know, if you have viruses, there's not a lot you can do to treat a plant virus except to get the plan out and not plant the same thing there for awhile. For non-commercial use, there's not a lot of treatments for bacteria. There are treatments for fungi and something else called Oomycetes that kind of act like fungi but aren't. And keep in mind that if you're going to use a fungicide, whether it's a conventional or an organic fungicide, you have to use it before the problem shows up. So it needs to be a situation where, you know, this has been a problem and you use it before it gets bad. Because if I have a maple tree my yard that gets Maple Tar Spot pretty much every year. If I wait until those black spots show up The fungus has already done what that fungus is going to do. I can't make those tar spots go away. They're not going to heal up. That's not going to prevent it for the next year. And you have to do something like that earlier in the year. And if you do spray something, make sure that what you're spraying effects the fungus that you want to kill and that its is okay for the host plant that you're using. Because if I use a fungicide, but it's not one that will kill maple tars. Even if I do it at the right time. If I use a fungicide on the tree that's not approved for maple tar spot. It's not gonna do anything about the maple tar spot And then I just wasted a lot of time and money and a lot of fungicide out in the environment that didn't need to be there in the first place. So make sure that you're using it for what it's registered for, that it's approved to not harm your plant, and that you're following all the instructions. Those little, teeny, teeny tiny words... get out your magnifying glass, get out your phone and read those because that really is important for actually preventing the problem and not hurting your plan. Because that's the worst to harm the plant. [Abby} Yeah. One of the things you said that I'm ruminating on is that just like pausing and taking a step back and looking. And last year I know we had Adi Palmer on who walked us through a lot of observational practices in the garden, which of course with COVID, some of us might have had more time to just be observational in the garden, but just building those skills of practicing, noticing to catch things on the early side so that you can do some of those preventative practices before it's gotten super out of control. And again, like I think we very often just Google, find the first solution, go do it rather than really thinking through goals. Really thinking through, you know, is this something that I can live with that I need to do something about or is it something that the plant will have served its purpose by the time this disease kind of takes it entirely. I mean, there's there's always kind of a certain amount of blight at the end of the season with tomatoes. And usually it's at a point where the tomatoes are starting to peter out anyway. So it's that balance of thinking about what are my goals and priorities. And will addressing this at this point in this way give me that outcome. [Isabel] And I think it brings up something that we've talked about. Just writing things down to use next year and to learn from in your garden. [Abby} Remembering where you planted the thing that was diseased and not planting the same thing the next year. Garden plans are so great to look back on, [Isabel] and if you do... write it down that year! There you go. [Lori] And that is especially if you're working with a vegetable garden, there's always next year. [ Abby] So we're wondering if you could share. I know we talked a little bit about where people might go wrong of treating the problem after it's already become too much of a problem. But are, there are some other common errors that people make in thinking about plant pathogens that we should be cautious to avoid? [Lori} I haven't mention this yet So far we have been talking about disease And because of my background I always speak about fungi, bacteria and viruses. not all disease is caused by something that is alive. A lot of diseases are caused by non-living or what we call abiotic situations. So, you know, too high or too low of light, poor water management, salt, all those things can cause symptoms that sometimes look like the things that are caused by these living things. So, you know, if, if something is dying because it's salt damaged, there's no amount of fungicide in the world that's going to make that better. So that's just wasted treatment and that's kind of the thing want to avoid. So considering all of the options, you're in, stepping back again and looking at that situation can be really helpful. Then the other thing is just making sure that you really thought through it before you treat. A lot of times we get pictures of plants or we're asked to help with something and you're somebody who's done a lot of treatments or maybe some home remedies. And a lot of us are really damaging to plants. And so we'll get to a place where we can't tell what the original problem was because there's just damage piled on damage . So yes, so that i just that that stopping and thinking through it and analyzing it really before that, before you get to that action point. I think that's a big thing. [Isabel] Do you have any helpful tips for distinguishing between like things that might be caused by a biotic thing or an abiotic thing? [Lori] Well, I guess especially if it's your own plant, is looking back and thinking about that history, right? Yeah. So do you have brown spots on your lawn and they're right next to the sidewalk or a place where, you know, that receives a lot of foot traffic or salts, you know, just thinking about the history of what has happened. So it can be a key indicator. Yeah, I think that probably would be the most important thing. Thinking about any changes that have happened to the plant. And considering that those changes may not be things you've done to it. So maybe some limbs fell off a tree and the area's getting more sun than it was getting before. So any sort of change like that can cause some of that damage. That's that's abiotic. [Isabel] Yeah, I feel like it's taking a step back and not because when people see damaged state like zone in on it. Just taking a step back and looking at the whole system and what the environment is like, because the environment could be causing it. [Lori] That big picture is really important. [Abby] And I remember a couple of weeks when we talked about beneficial insects. Just the conversation around pausing to notice what's going on and seeing if you're if you pause in that space long enough, do you see a little bug that's causing those spots or bringing something in, or is that something that is more systemic or pathological sort of thing? So just those observational skills for sure. [Isabel] Yeah. But it can be helpful to look closely to right Lori? I go and look good. [Lori} Yeah, so if you have like a magnifying lens or a like a little microscope or something like that. Little things that you can put on smartphones now that you can get close up. And sometimes you can see things that look like fungal structures. You know, powdery mildew is a good example. A lot of times with these diseases the fungus is mostly inside of the plant and you have to be harder to see. but Powdery Mildew is actually growing on top of the plant and you don't have to have a high powered microscope to get down and to be able to see the fungal structures that are growing on top of the leaves. So yeah, so sometimes you can see some of those fungal structures that would indicate that it's a disease. That's it. The living thing cause this disease. [Abby] Awesome. So we're getting a couple of questions from the audience. I wanted to make sure we touched on... and a number of them have to do with cucumbers and some of the various diseases that cucumbers come with. Kind of cucumber wilt, powdery mildew. Can you talk about any specific preventative practices for cucumbers are things that might be afflicted by similar pathogens. [Lori] Well, like I said, if you, if you know you've got a particular issue, when you've got the plant there trying to parse out what is causing that issue at that time. And, you know, and then I have something like a cucumber downy mildew has started showing up in the fall, you know, and that's as that some of these diseases accumulate over the season. It might be you may not get a lot of late season cucumbers, just sort of acknowledging that is important. And then yeah, trying to pick out cucumbers, maybe picking out some cucumber seeds looking for that resistance. I'm not exactly sure what all kinds of resistance exist, with cucumbers. And then if you are having a persistent problem, you can do something like rotate it out to a different area. You know, maybe it's something that's existing in that space more as well as you might also need to use ... you've identified that is something that's caused by fungus, then there might be some fungal fungicide treatment early in the season that can help prevent that problem. But it's gonna depend on what exactly the disease is, figuring out what it is, and then figuring out that IPM strategies for managing it. [Isabel] Another question that came in that I thought brought up a good point. It's like when is a good time to, to look for signs of disease? Because the question was, if you know you had a disease and you clean up that debris there, is that too late to